Marking methods for tracking and recapturing snakes around the world: An integrative review

Abstract

Mark-recapture studies using marking techniques are crucial for understanding the ecology and behavior of snakes. This review aims to identify and compare the most common marking methods employed in snake ecology research, from traditional techniques to modern, innovative approaches. These methods facilitate global research on snake individualization, tracking, and recapture. We evaluated 1.533 papers encompassing over 482 species, the reviewed studies span 78 countries, reflecting a wide geographical distribution of snake marking research. The United States, Canada, Australia, and Brazil have contributed the most studies. Among the most widely used methods, radio telemetry remains essential for despite tracking its invasiveness and associated risks for snake’s welfare. More recent innovations, such as fluorescent powder and elastomer marking, offer cost-effective, non-invasive alternatives, applicable across diverse species and habitats. Microchipping, a well-established method, continues to be a reliable option for long-term monitoring, with successful recaptures documented after over 30 years. Natural marks, recognized through photographs and drawings. This paper the importance of continually refining snake marking techniques to balance research efficacy with animal welfare. Future advancements should focus on improving durability, facilitating recapture, and minimizing disruptions to snake ecology, health, and behavior, ultimately supporting more effective autecological and population studies.

Key words
Ecological research; Mark-recapture studies; Snake marking techniques; Snake welfare

INTRODUCTION

Marking individuals in animal populations is essential for ecological research, providing insights into population ecology, behavioral biology, autoecology, and population genetics, among other fields (Murray & Fuller 2000, Janecka et al. 2021, Haskins et al. 2024). Individual identification enables researchers to monitor survival rates, reproductive success, migration patterns, population size, growth rates, and demographic changes over time (Silvy et al. 2005, 2012). Furthermore, it facilitates behavioral studies by tracking movement patterns, foraging strategies, mating behaviors, and social interactions (Murray & Fuller 2000). In addition, individual marking plays a crucial role in genetic studies, allowing researchers to trace lineages across generations and assess genetic diversity, gene flow, inbreeding, and the effects of genetic variation on population fitness (Basavaraju et al. 1998, Hamilton 2021).

Snakes have been recognized as an important model for ecological research for over two decades (Shine & Bonnet 2000). With more than 4,177 described species, they exhibit remarkable morphological diversity in terms of size and shape and inhabit a wide range of environments (Uetz et al. 2025). As key components of trophic networks, snakes play an essential role in ecosystem dynamics (Greene 1997, Title et al. 2024). However, their secretive habits make them difficult to locate in the wild, posing challenges for population and community monitoring (Fitch 1987). The Neotropical region harbors the world’s highest diversity of herpetofauna (Guedes et al. 2017), whereas temperate regions often exhibit higher abundance of specific snake species, particularly those that hibernate in aggregations (Skinner & Miller 2020, Turner 2023).

Since the 1930s, various marking techniques have been employed to identify individual snakes. These methods include scale removal to create permanent scars (Blanchard & Finster 1933, Brown & Parker 1976) and passive integrated transponders (PIT tags) or microchips, which are subdermally injected and contain unique numerical codes (Gibbons & Andrews 2004). Other commonly used techniques include telemetry, which relies on radio signals for individual tracking (Madrid-Sotelo & Valdivia 2008), and natural pattern recognition based on spot arrangements and scale configurations (Bentes et al. 2017). The choice of marking method depends on study objectives (e.g., short-term vs. long-term monitoring) as well as the species’ ecological and behavioral traits.

Given the widespread use of individual marking in snake research, a comprehensive review of mark-recapture studies is necessary. Here, we address the following key questions:

(1) What are the different marking methods used for snakes? (2) Which methods are most commonly employed, and which are the most invasive? (3) Are most studies concentrated in temperate regions due to higher likelihood of aggregating behavior, which facilitates marking? (4) Are recapture rates higher in temperate regions, where snake abundances are generally greater? (5) Are Dipsadidae and Colubridae the most studied families due to their high abundance?

Additionally, we provide a geographical overview of snake-marking studies, identifying the most frequently studied species and analyzing temporal trends in the use of marking techniques that have been employed for over 90 years.

MATERIALS AND METHODS

We conducted a systematic literature search to address the question: “What are the marking methods used for individual identification, tracking, and recapture in snake research worldwide?” Our approach followed the Population, Intervention, Comparison, Outcome, and Study Type (PICOS) approach, which is recommended for bibliographic reviews and widely applied in Evidence-Based Practice (EBP) (Santos et al. 2007). In this framework, snakes represent the population, marking techniques serve as the intervention, and comparisons are made at the species level. The outcome includes evidence related to adverse reactions, features, costs, and durability of the methods. We included field and laboratory studies but excluded other review articles with thematic overlap.

Between April 2023 and June 2024, we systematically searched for studies that employed snake-marking techniques using the following platforms: Google Scholar, Scopus, Web of Science, and ResearchGate. Additionally, we examined all volumes of the following journals available online: Acta Herpetologica; Basic and Applied Herpetology; Boletín de la Asociación Herpetológica Española; Herpetologia Brasileira; Herpetological Bulletin; Herpetological Monographs; Herpetological Review; Herpetology Notes; Herpetozoa; Journal of Herpetology; South American Journal of Herpetology; Amphibia-Reptilia; Salamandra; Russian Journal of Herpetology; The Herpetological Journal; and Herpetological Conservation and Biology.

To maximize coverage, we searched for articles using the following keywords in English, Portuguese, and Spanish:

English: “Herpetofauna” AND “recapture”; “Herpetofauna” AND “mark-recapture”; “Snake” AND “recapture”; “Snake” AND “telemetry”; “Snake” AND “microchip”; “Snake” AND “PIT-Tags”; “Snake” AND “visible implant elastomer”; “Snake” AND “Thread Bobbin”; “Tagging” AND “Snake”.

Portuguese: “Herpetofauna” E “marcação”; “Serpente” E “recaptura”; “Serpente” E “marcação”; “Serpente” E “carretel”; “Serpente” E “telemetria”; “Serpente” E “elastômero”; “Serpente” E “microchip”.

Spanish: “Herpetofauna” Y “marcación”; “Serpiente” Y “carretes de hilo fijados”; “Serpiente” Y “telemetría”; “Serpiente” Y “elastómero”; “Serpiente” Y “microchip”; “Serpientes” Y “marcación”.

Because not all studies explicitly mention the marking technique in their titles, title screening was not used as an inclusion criterion. Instead, we evaluated articles based on their abstracts and methodologies. We included all studies that employed marking techniques for snake identification in either wild or captive settings, regardless of language.

Taxonomic names were reviewed and updated according to the Reptile Database (http://www.reptile-database.org/) (Uetz et al. 2025). However, we followed Zaher et al. (2019) in recognizing Dipsadidae as a distinct family. We also included some gray literature — such as unpublished reports, monographs, dissertations, and theses — because these sources often provide information on marking and recapture that is not found in peer-reviewed publications.

Exclusion Criteria

We excluded references that met any of the following conditions:

(1) articles in which the term “snake” referred to a different taxonomic group; (2) articles that mentioned participation in a mark–recapture study without describing the methodology; (3) articles that used the term “mark” in contexts unrelated to individual tagging (e.g., genetic markers, natural body patterns, captive experiments, or references to other taxa); (4) bibliographic review articles; (5) gray literature sources that were later published in peer-reviewed journals; (6) studies in which the focus was on the prey or predators of snakes rather than on the snakes themselves; (7) studies that did not report the snake species studied; (8) studies that did not specify the marking technique used; (9) studies that marked herpetofauna groups other than snakes; (10) studies that only proposed marking and recapture techniques for future research; and (11) studies using movement simulation rather than actual marking techniques.

Data Extraction

For each eligible reference, we recorded the species studied, marking technique, country of study, and study objective. When available, we also collected data on the research duration, study conditions (wild vs. captive), number of captures, recapture rates, and body sizes of marked individuals.

All articles, scientific notes, monographs, unpublished dissertations, theses, books, book chapters, and technical reports containing relevant descriptors were saved in a database. To enhance transparency and readability, we followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA 2020) guidelines (Lima et al. 2018, Page et al. 2021), which provide a standardized checklist and flowchart for systematic review studies.

RESULTS

From the 1,845 studies identified, screened, and fully reviewed, we selected 1,533 studies for inclusion (Figure 1). These comprised 3 books, 29 book chapters, 117 gray literature sources, and 1,384 journal articles (see Supplementary Material – Appendix SI: Complete list of studies included in the review). The selected studies were published in nine languages: English (96.60%), Portuguese (1.56%), Spanish (0.52%), French (0.52%), German (0.39%), Italian (0.19%), Dutch (0.06%), Japanese (0.06%), and Polish (0.06%). The studies spanned 78 countries worldwide, from 1933 to 2024 (Figure 2). However, the 27 articles published in 2024 were excluded from the bibliometric analysis, as they only represent data from the first six months of the year (see Figure 2).

Figure 1
Flowchart of the number of articles found and selected after applying the inclusion and exclusion criteria, following the PRISMA methodology.

Figure 2
Bibliometric analysis of the distribution of works in relation to years of publication.

In total, 482 snake species (representing 11.71% of all described species worldwide) were studied using individual marking techniques. These species belonged to 15 families, 196 genera, and 55 subspecies. The most frequently studied families were Dipsadidae, Colubridae, and Viperidae (Figure 3). Among the 15 families, nine lacked subfamilies, while six contained two to seven subfamilies:

Figure 3
Pie chart indicating species richness proportion by snake family in our literature review of marking techniques used to individualize specimens collected in the field worldwide. The chart represents data on 1.384 articles, 3 books, 29 book chapters, 117 grey literature and a total of 482 species.

(1) Boidae (Boinae, Calabariinae, Charininae, Erycinae, Ungaliophiinae, Candoiinae, Sanziniinae); (2) Colubridae (Colubrinae, Ahaetuliinae, Grayiinae); (3) Dipsadidae (Xenodontinae, Carphophiinae, Dipsadinae); (4) Elapidae (Hydrophiinae, Laticaudinae); (5) Typhlopidae (Typhlopinae, Asiatyphlopinae); and (6) Viperidae (Crotalinae, Viperinae, Azemiopinae).

Some Dipsadidae genera remain unassigned to any subfamily (Boundy 2020, Uetz et al. 2025). However, not all subfamilies were represented in the marking and recapture studies (Table I).

Table I
Families that have subfamilies of the species sampled in marking and recapture work and the representation of the percentage of recorded species compared to the number of species in the families and subfamilies. *Not included – number of species sampled from genera of the Dipsadidade family that are not included in subfamilies.

Family/Subfamily	Number of species	Number of sampled species	Family percentage %	Subfamily percentage %
Boidae	67	19
Boinae	37	15	22.36	40.54
Calabariinae	1	1	1.49	100
Charininae	4	2	2.98	50
Erycinae	13	1	1.49	7.69
Colubridae	875	113
Colubrinae	794	78	8.91	9.82
Ahaetuliinae	77	3	0.34	3.89
Grayiinae	4	1	0.11	25
Dipsadidae	804	129
Xenodontinae	326	82	25.15	10.19
Carphophiinae	4	3	0.37	75
Dipsadinae	456	37	4.60	8.11
Not included*	18	7	0.87	38.88
Elapidae	410	30
Hydrophiinae	207	27	6.58	13.04
Laticaudinae	8	3	0.73	37.5
Typhlopidae	429	4
Typhlopinae	335	2	0.46	0.59
Asiatyphlopinae	132	2	0.46	1.51
Viperidae	400	80
Crotalinae	294	59	14.75	20.06
Viperinae	100	21	5.25	21

A total of 14 marking methods were identified, with some further subdivided based on application technique or intended use (see Table II). Authors employed one to four marking methods per study, applied to one or more species. The distribution of marking method usage was as follows:

Table II
List of individual snakes marking methods used for tracking and recapture in autoecological and population studies carried out around the world. R- Richness of species used in each method. C – Number of countries with studies using each marking. N- Number publications recovered. Reference: oldest and most current reference of works found with each method. *For this paper, we use the term “telemetry” for all marking methods that use a radio transmitter.

Nº	Techniques	R	C	N	Description	Reference
Tracking
1	Telemetry *	189	47	611	Tracking by a radio transmitter (internal or external) via an antenna.	Osgood 1970, Reynolds et al. 2024
1a	Ingestion	33	12	31	Insertion of the radio transmitter through power supply, offered or forced.	Osgood 1970, Champagne 2022
1b	Surgery	151	38	491	Insertion of the radio transmitter through a surgical incision, with the option of inserting only the transmitter and antenna outside the body or both inside the body.	Fitch & Shine 1971, Reynolds et al. 2024
1c	Externally attached radio-transmitters	36	13	43	Attach the radio transmitter to the snake’s body with glue, tape, thread or surgical thread. The latter is done by making two holes with a catheter at the ends of the body, through which the thread passes inside.	Gent & Spellerberg 1993, Champagne et al. 2024
1d	Bio-Loggin	8	4	8	Fixing a radio transmitter with a GPS attached, which can be internal or external.	Bonnet 2012, Gerke et al. 2021
1e	Subdermal stitch	10	6	11	The transmitter antenna is surgically inserted into the snake’s body and the transmitter is attached externally to the snake.	Ciofi & Chelazzi 1991, Howarth et al. 2023
1f	Not described	25	7	32	It does not describe which category of telemetry was used.	Blem & Blem 1995, Sandfoss et al. 2024
2	Ultrasonic pressure transmitters	2	2	3	Ultrasonic pressure transmitter is inserted or attached to sea snakes that are tracked by a hydrophone.	Rubinoff et al. 1986, Burns & Heatwole 1998
3	Radioisotopes	7	2	5	The snake is marked with a radioactive chemical element and tracked with a Geiger counter.	Hirth et al. 1969, Bonnet 2012
4	Fluorescent powdered pigments	12	2	2	The snake is covered with a non-toxic fluorescent powder leaving a trail visible under ultraviolet light.	Furman et al. 2011, Lima et al. 2021
5	Thread bobbins	36	4	12	Attach a thread bobbins to the snake’s body and tie the loose end to the starting point.	Ávila-Villavegas 2006, Banci 2023
6	Microchip (passive integrative transponders- PIT tag)	15	1	5	The authors used an extender antenna from the microchip reader to track the snake.	Oldham et al. 2015, McKenzie et al. 2021
Recapture
6	Microchip (PIT tag)	215	50	468	Transponders implanted subdermally, which provide a unique numbering, where the numerical code is read with a specific reader.	Camper & Dixon 1988, Reynolds et al. 2024
7	Scale clipping	330	44	480	Partial or total clipping of the scales forming codes.	Dalrymple & Reichenbach 1881, Skinner et al. 2024
7a	Partial scale removal	42	5	18	Removal of the lower part of the scale allowing regeneration and leaving no scar.	Saint Girons 1981, Barbosa et al. 2022
7b	Total scale removal	287	42	462	Complete removal of the entire scale, resulting in a scar present even after the skin has been replaced.	Dalrymple & Reichenbach 1881, Skinner et al. 2024
8	Fluorescent elastomer	66	3	17	Fluorescent polymer applied subdermally to dorsal and/or ventral scales, with different color options, visible under ultraviolet light. Forming numerous codes.	Stanley & Trauth 2007, Amaral et al. 2022
9	Electric tattooing	4	1	1	Application of ink with needles and tattoo machine forming unique codes.	Woodbury et al. 1948
10	Freeze or heat branding	10	4	19	Cool or heat an iron with shapes or numbers and apply it under the skin, changing the pigmentation of the scale without altering the integument, forming permanent marks.	Clark 1971, Bonnet 2012
11	Cauterization	102	12	116	Burning off the scale with a cauterizer or soldering iron creating a permanent coded scar.	Weary 1969, Nguyen et al. 2023
12	Natural marks	60	42	141	Recognition of the individual through the pattern of spots on the body, arrangement of scales and/or scars.	Carlstrom & Edelstam 1946, Allain et al. 2024
13	Paint	65	23	129	Paint numbers or shapes on the snake’s body for quick recognition from a distance.	Fitch 1960, Goméz unpublished data
14	Tag	12	4	17	Glue or sew etiquettes onto the snake’s body for quick recognition from a distance.	Thomas & Eklund 1962, Jones et al. 2017

(1) 68% of studies (n = 1,005) used a single marking method; (2) 26% (n = 386) used two methods; (3) 5% (n = 71) used three methods; (4) 1% (n = 15) used four marking methods simultaneously.

Of the 78 countries where studies using snake marking techniques have been conducted, 16 countries have 10 or more publications (Figure 4). Studies have been carried out on all continents except Antarctica, with notable contributions from the United States (n=736), Canada (n=151), Australia (n=122), Brazil (n=70), France (n=61), Italy (n=51), the United Kingdom (n=33), Japan (n=21), Thailand (n=20), Sweden (n=19), Mexico (n=18), India (n=16), Nigeria (n=13), Switzerland (n=12), Panama (n=10), and Spain (n=10) (Figure 4). Four methods—telemetry, microchipping, scale clipping, and natural markings—have been used in more than 30 countries. The six most widely used methods, with over 100 studies each, were radio telemetry, microchips, scale clipping, natural markings, paint, and cauterization (Table III).

Table III
Distribution between works by methodology. The captions represent: Species - richness of species studied with each method; Country - number of countries in which a certain method was used; Papers - number of references in which each methodology was used.

Technique	Papers	Species	Country
Telemetry	650	185	46
Microchip	479	213	44
Scale clip	487	326	46
Natural marks	148	61	38
Paint	131	65	23
Cauterization	116	100	13
Thread bobbins	12	36	4
Freeze or heat branding	19	11	4
Fluorescent elastomer	17	59	3
Tag	17	11	3
Ultrasonic transmitters	3	2	2
Radioisotopes	5	7	2
Fluorescent powdered	2	12	2
Tattooing	1	4	1

Figure 4
Global distribution of countries with published mark–recapture studies involving snakes. Colors represent the number of published studies per country identified in the systematic review, with warmer colors indicating a higher number of publications. Countries without records correspond to locations where no eligible studies were identified. Data include all studies retrieved regardless of publication year.

Africa

On the African continent, snake mark-recapture studies were recorded in only five countries, with Nigeria having the highest representation, with more than 10 studies (See Figure S1). Three countries had records of only one species: Cameroon with Python sebae (Pythonidae), Ivory Coast with Bitis rhinoceros (Viperidae), and Kenya with Psammophis mossambicus (Psammophiidae). South Africa had four studied species, Bitis arietans, B. schneideri, Python natalensis, and Limaformosa capensis, of the Viperidae, Pythonidae and Lamprophiidae families. Nigeria exhibited the highest species diversity on the continent, with 29 species studied across eight families: Calabariidae (1), Colubridae (3), Dipsadidae (1), Elapidae (4), Lamprophiidae (10), Natricidae (3), Pythonidae (1), and Viperidae (6). All species were cited in a maximum of two works, with the exception of Bitis arietans which was studied in three articles, with only one form of marking (telemetry by surgery). The B. schneideri was the species used in three different techniques (total scale removal, external telemetry and surgery), and in three other species two marking techniques were used B. rhinocerus (microchip and natural marks); B. gabonica (total removal of scales and telemetry by surgery) and Dendroaspis jamesoni (total removal of scales and paint).

Asia

Mark-recapture studies were recorded in 16 Asian countries, with Japan (21 studies) and Thailand (20 studies) leading in research volume (see Figure S2).

Six countries had mark-recapture studies on only one species: Ophiophagus hannah (Elapidae) in Bhutan and Nepal, Naja sputatrix (Elapidae) in Indonesia, Montivipera latifii (Viperidae) in Iran, Montivipera raddei (Viperidae) in Armenia, and Oocatochus rufodorsatus (Colubridae) in North Korea.

Eight other countries had six or fewer studied species. Israel recorded two species, Cerastes cerastes and Echis coloratus, both from the Viperidae family. South Korea had three species: two from Colubridae (Orientocoluber spinalis and Elaphe schrenckii) and one from Viperidae (Gloydius ussuriensis). Malaysia had four species across four families: Colubridae (Boiga nigriceps), Hydrophiidae (Hydrophis schistosus), Viperidae (Calloselasma rhodostoma), and Elapidae (Laticauda colubrina). China recorded four species, all from Viperidae (Gloydius shedaoensis, Protobothrops mangshanensis, Trimeresurus albolabris, and T. stejnegeri). Taiwan had four species across three families: Colubridae (Oligodon formosanus), Natricidae (Trimerodytes annularis and T. percarinatus), and Viperidae (Trimeresurus stejnegeri stejnegeri). India recorded five species from four families: Colubridae (Cerberus rynchops), Elapidae (Ophiophagus hannah), Pythonidae (Python molurus), and Viperidae (Daboia russelii and Macrovipera lebetinus). Singapore had six species, with Colubridae (Cerberus rynchops, C. schneiderii, Chrysopelea paradisi) and Homalopsidae (Cantoria violacea, Fordonia leucobalia, and Gerarda prevostiana).

Japan was the second most diverse country in Asia, with 11 species across five families. Colubridae was the most represented (five species), followed by Natricidae and Viperidae (two species each), and Elapidae and Xenodermatidae (one species each). The most studied species was the Japanese striped snake (Elaphe quadrivirgata), cited in 10 studies. Thailand had the highest diversity in both species (12) and families (7), including Elapidae (4 species), Viperidae (2), Homalopsidae (3), Colubridae (1), Natricidae (1), Cylindrophiidae (1), and Pythonidae (1).

Central America and the Caribbean

Thirteen Central American countries had snake marking studies, with Costa Rica and Panama having the highest numbers (See Figure S3).

In Antigua and Barbuda, all studies focused on the endemic Antigua racer (Alsophis antiguae, Colubridae), with additional research on Boa constrictor (Boidae), Clelia clelia (Dipsadidae), and Pantherophis guttatus (Colubridae). The Bahamas had only one studied species, the Bahamas racer (Cubophis vudii, Colubridae). In Belize, research was concentrated in the capital and focused on three species: Boa constrictor, Oxybelis aeneus, and Spilotes pullatus (Colubridae). Saint Lucia had a single study on the Saint Lucia Racer (Erythrolamprus ornatus) an endemic species to the country that covered the entire island. The British Virgin Islands had a single study on the Puerto Rican racer (Borikenophis portoricensis, Dipsadidae), a species restricted to the Virgin Islands and Puerto Rico. Puerto Rico recorded studies on four species across three families: Boidae (Boa constrictor and Chilabothrus inornatus), Dipsadidae (Borikenophis portoricensis), and Colubridae (Pantherophis alleghaniensis). Cuba, Honduras, Jamaica, Nicaragua, and the Turks and Caicos Islands each had mark-recapture studies on a single species, all from the Boidae family: the Cuban boa (Chilabothrus angulifer), the boa constrictor (Boa constrictor), the Jamaican boa (Chilabothrus subflavus), the Central American boa (Boa imperator), and the Turks Island boa (Chilabothrus chrysogaster), respectively.

Finally, Costa Rica had the highest species richness (46 species) among Central American countries, with Dipsadidae (35 species) being the most represented, followed by Viperidae (5), Colubridae (3), Boidae (2), and Elapidae (1). Panama followed with 13 species across five families, with Dipsadidae being the most abundant (9 species), while Boidae, Colubridae, Elapidae, and Viperidae had one species each.

Europe

Europe had the highest number of countries (28) with recorded mark-recapture studies (see Figure S4), totaling more than 270 studies. France (61) and Italy (51) had the highest numbers, each exceeding 50 studies. Six countries were represented by one work each, where five had only one species: Albania (Natrix tessellata), Cyprus (Natrix natrix), Jersey (Natrix helvetica), Latvia (Coronella austriaca), Norway (Coronella austriaca) and Ukraine. France (61), Italy (51), England (33), Sweden (19), Switzerland (12) and Spain (10) were the countries with the most works found and together they have 38 species cited in the marking and recapture works, distributed in six families: Boidae (1); Colubridae (13); Elapidae (6); Natricidae (6); Pythonidae (1) and Viperidae (11). The remaining countries have between two and nine works (see figure 11). A total of 11 species had more than 10 related works, with two species of the Viperidae family having the most studies carried out, Vipera berus (38) and V. aspis (34). Followed by Natrix natrix and Hierophis viridiflavus with 30 manuscripts each, Coronela austriaca (28), Zaenis longissimus (25), Natrix tessellata (22), Laticauda saintgironsi (13) and three species with 12 publications each (Emydocephalus annulatus, Laticauda laticauda e Natrix helvetica).

North America

North America had the largest number of studies on snake marking and recapture. The United States led with 736 studies, covering nearly all states, including Guam (Oceania). Canada followed with 151 studies, and Mexico had 18 publications (See Figure S5).

The United States had the highest diversity of studied species (119), spanning nine families. The most frequently studied species were Crotalus horridus (75 studies), Thamnophis sirtalis (69), and Coluber constrictor (65). The most diverse families were Colubridae and Natricidae (34 species each), followed by Viperidae (29), Dipsadidae (11), Elapidae (4), Boidae (2), and single representatives of Lamprophiidae, Pythonidae, and Typhlopidae. Guam, an island territory of the U.S., recorded only one specie: Boiga irregularis.

In Canada, 26 species were recorded, with Thamnophis sirtalis being the most studied, accounting for 31% of all Canadian studies and appearing in more than 45 publications. Four families were represented: Natricidae (10 species), Colubridae (9), Dipsadidae (4), and Viperidae (3).

Mexico had mark-recapture studies on 15 snake species across four families (Colubridae, Dipsadidae, Natricidae, and Viperidae). Viperidae was the most represented, comprising 73.33% of studied species. The rattlesnakes Crotalus catalinensis and C. willardi were the most frequently studied species, each appearing in three studies.

Oceania

Three countries in Oceania conducted mark-recapture studies on snakes: Fiji, Papua New Guinea, and Australia. While Fiji and Papua New Guinea had single-species studies on the sea krait (Laticauda colubrina, Elapidae) and the green python (Morelia viridis, Pythonidae), respectively, Australia ranked third globally in the number of studies (121), with research spanning all states (see Figure S6). In Australia, 43 species across three families were studied, with Elapidae being the most represented (27 species), followed by Pythonidae (14) and Colubridae (10).

South America

Among the eight South American countries represented in the dataset, Brazil had the highest number of studies, with São Paulo (Southeast), Paraíba (Northeast) and Rio Grande do Sul (South) having the most studies (Figure 5). A total of 158 snake species were studied in mark-recapture research in Brazil, representing 36.32% of the country’s known snake diversity and spanning seven families. Seven species were investigated in 10 or more studies, with Boa constrictor leading (15 studies), followed by Chironius flavolineatus (14), Crotalus durissus (13), Philodryas olfersii (11), and Micrurus ibiboboca, Oxybelis aeneus, and Oxyrhopus trigeminus, each appearing in 10 studies. Among families, Dipsadidae was the most represented (93 species), followed by Colubridae (29), Viperidae (15), Elapidae (10), Boidae (8), and Aniliidae (1 species).

Figure 5
Geographic distribution of Brazilian states with published snake mark–recapture studies. Colors indicate the number of papers conducted in each state identified in the systematic review, with warmer colors representing a higher number of studies. States shown without color indicate no eligible publications.

Other South American countries had fewer than 10 studies each, covering at most two states per country (see Figure S7). Peru ranked second in both the number of studies and species diversity, with 11 species across four families. Dipsadidae was the most represented family (six species), followed by Colubridae and Viperidae (two species each) and Boidae (one species, the green anaconda, which was the most frequently studied). In Argentina, only two species were studied: Boa constrictor occidentalis (Boidae) and Bothrops alternatus (Viperidae). Bolivia had mark-recapture studies on two species of anacondas (Eunectes beniensis and E. murinus, Boidae), while Chile recorded a single species, the Chilean green snake (Philodryas chamissonis). Ecuador lacked mainland mark-recapture studies, with the only recorded research occurring in the Galápagos Islands on the Galápagos runner (Pseudalsophis biserialis biserialis). Colombia had a single study in the Meta region on the Hallowell coffee snake (Ninia atrata, Dipsadidae). In Venezuela, the only recorded study focused on the green anaconda (E. murinus) in the state of the Apure.

Figure 6
Distribution of snake mark–recapture studies according to monitoring duration. Bars represent the number of papers classified by the length of the study period, illustrating the prevalence of short- and long-term monitoring efforts.

Focus of studies

Of the 482 snake species studied using at least one marking method, 40.04% (n = 193) were referenced in only a single publication, utilizing between one and three marking techniques (see Table SI). Among the 1,533 studies included, we identified 387 focused on specific aspects of snake biology, such as: Reproduction in wild and captive environments (Macartney & Gregory 1988, Kian et al. 2011, Angarita-Sierra & López-Hurtado 2020); Same-sex courtship and mating behavior (Lee et al. 2010, Metcalf et al. 2020); Sexual dimorphism (Strine et al. 2015, Shine & Goiran 2021); Parthenogenesis (Jordan et al. 2015); Multiple paternity (Nanni Geser & Ursenbacher 2022); Genetic analyses (King & Lawson 1995, Manier & Arnold 2005, Janecka et al. 2021); Thermoregulation (Amiel & Wassersug 2010, Bovo et al. 2012); Effects of invasive plant management on snake shelter sites (Carter et al. 2017); Diet studies (Capula et al. 2006, Perkins et al. 2020); Defensive behavior and thanatosis (death-feigning) (Kissner et al. 1997, Golubović et al. 2021); Physiological research (Holding et al. 2014); Microbiology, including ophidiomycosis and fungal diseases (Allender et al. 2016, McKenzie et al. 2021); Locomotion and kinematics, including flight trajectory (Socha et al. 2005, 2010); Heavy metal contamination, such as mercury exposure (Lemaire et al. 2018, Haskins et al. 2021); Dwarfism in island populations (Vanek & Burke 2019).

Approximately 17 studies explicitly focus on invasive snake species, as their primary objective, addressing the monitoring and management of these populations, as well as evaluating ecological impacts, habitat selection, and population control strategies. Boiga irregularis is the most extensively studied invasive snake species in the United States, with 11 published articles; among these, four studies specifically investigated population control using toxic baits (Savarie et al. 2001, Siers et al. 2020, Goetz et al. 2021, Nafus et al. 2020a). Another invasive species for which mark–recapture approaches were applied in the United States is Python bivittatus, including studies focused on population monitoring (Nafus et al. 2020b), trap testing (Reed et al. 2011), and the application of the “Judas technique” (Harvey et al. 2008, Smith et al. 2016). In Australia, one study assessed the ecological impacts of Stegnotus cucullatus on native species (Brown et al. 2013).

Additionally, 101 studies focused on the development and analysis of marking methodologies. Some significant and representative studies are: Hoefer et al. (2021) and Lukanov & Dyugmedzhiev (2023) assessed software for recognizing natural scale patterns in Cubophis vudii vudii and Vipera ammodytes; Bentes et al. (2017) explored the use of natural gular and ventral scale patterns to identify individuals in Helicops polylepis; Riley et al. (2017) compared three attachment methods (glue, tape, and subdermal sutures) for radiotransmitters in Sistrurus catenatus and Pantherophis guttatus; Smith et al. (2018) examined bio-logging technology to study the spatial ecology of Python bivittatus; Taggart et al. (2021) investigated the effects of microchip implants on growth in P. bivittatus; Tozetti & Martins (2007) described an external radiotransmitter and spool-tracking technique as a less invasive alternative to surgically implanted telemetry devices; Early experimental marking techniques included Hundnall (1982), who stitched beads onto the tails of Sistrurus miliarius, and Pough (1970), who used a Buttoneer® tagging device on Thamnophis sirtalis; Oldham et al. (2016) tested a modified microchip method using Regina septemvittata, incorporating an extended antenna for active signal detection, mimicking telemetry tracking.

Finally, the remaining 1,045 studies addressed broader aspects of natural history at the individual, population, and community levels. These studies included: Diet and predation risks (Colbert et al. 2014, Barbosa et al. 2022a); Parental care (Greene et al. 2002); Defensive behaviors, including thanatosis (Gregory et al. 2007, Golubović et al. 2021); Water acquisition behavior (Sasaki & Duvall 2003); Rattlesnake rattle function (Kissner et al. 1997); Thermoregulatory strategies (Lillywhite 1980); Juvenile behavior and development (Cobb et al. 2005); Sex-based behavioral variation (Roth & Lutterschmidt 2011); Climbing and arboreal behavior (Saenz et al. 1996, Rudolph et al. 2004); Fire ecology and response to burns (Smith et al. 2001); Human-wildlife interactions (Spencer et al. 2015); Species inventories and biodiversity assessments (Olson et al. 2016, Barbosa et al. 2022b); Demographic studies (Riedle 2014, Jones et al. 2017); Social behavior and aggregation (Skinner & Miller 2020, Turner 2023); Home range and habitat use (Alexander & Maritz 2015, Teffo et al. 2023); and Population and community monitoring (Alberts 2006, Baier & Wiedl 2010, Ernst et al. 2012, Diaz & Blouin-Demers 2017).

The duration of snake monitoring studies using marking techniques ranged from a few days to over six decades. The longest continuous study spanned 68 years, tracking a Natrix natrix population in the Stockholm region, Sweden (Elmberg et al. 2024). Additionally, three other studies exceeded 30 years of monitoring: Tully et al. (2020) conducted a 37-year study on Vipera ursinii in the Beaumont-du-Ventoux Commune, France; Todd et al. (2008) monitored Virginia striatula and Virginia valeriae in South Carolina, USA, for 36 years; Brown (2016) tracked a population of Crotalus horridus in New York for the same duration. These long-term studies primarily employed scale clipping, alongside techniques such as paint marking, cauterization, and natural scale pattern recognition. Despite being an invasive and historically old method (Blanchard & Finster 1933), scale clipping remains a cost-effective and reliable technique, still widely used today for both short-term and multi-decade population studies (Elmberg et al. 2024, Nafus et al. 2024).

In terms of monitoring duration, most studies (29.50%) lasted from a few days to one year. Another 23.36% spanned three to four years, while 15.14% lasted one to two years. Overall, 85.63% of studies were conducted over a period of ten years or less, while 10.18% extended beyond ten years. A small fraction (4.17%) of the collected references did not specify the duration of the study (Figure 7).

DISCUSSION

Among the studies involving snake marking for recapture, 22 papers reported no successful recaptures despite employing methods such as cauterization, elastomer tagging, microchipping, painting, and partial or total scale clipping. These studies spanned monitoring periods ranging from less than one year to over 30 years, suggesting that the cryptozoic habits of snakes may contribute to the difficulty of recapturing individuals in the wild. Nevertheless, these studies documented between one and 159 captured individuals across one or more species. Additionally, 190 studies did not explicitly state whether recaptures occurred, while 33 studies were either isolated observations or laboratory-based research, where recapture was not applicable.

In contrast, 1,288 publications successfully recorded recaptures, with 1,270 studies reporting multiple recaptures of one or more individuals. Notably, two studies recorded more than 10,000 captures: Bonnet (2012) in New Caledonia, France, marked over 14,000 individuals of Laticauda laticaudata and L. saintgironsi using scale clipping, telemetry (bio-logging), radioisotopes, and iron branding, resulting in over 6,000 recaptures, and King et al. (2018) on islands in the United States captured 13,802 individuals of Nerodia sipedon insularum, marked using microchips and ink, with 6,200 recaptures. These large-scale studies spanned 1–10 years and 11–20 years, respectively, and highlight the importance of long-term monitoring in understanding snake populations. Such long-term efforts enable robust estimates of population parameters and reveal demographic patterns and individual life-history trajectories that would not be detectable in short-term studies.

A total of 70 studies reported capturing between 1,000 and 8,700 specimens, typically from multiple populations, using a range of techniques (cauterization, branding, natural marks, microchipping, scale clipping, paint, and telemetry). These studies were conducted across 14 countries, primarily in temperate regions, with exceptions in Antigua and Barbuda (tropical), Guam (tropical), and parts of Australia (subtropical) (see table IV).

In temperate zones, hibernation in aggregations may facilitate high capture rates and increase the likelihood of recaptures (Gray 2013, Luiselli et al. 2018). Conversely, in tropical regions, high capture rates may reflect targeted conservation efforts. For example: In Antigua and Barbuda, Daltry et al. (2017) recorded over 1,000 individuals of the critically endangered Alsophis antiguae over a 20-year monitoring period, assessing population fluctuations and reintroduction success following the eradication of the invasive black rat (Rattus rattus), a major predator. Moreover, in Guam, the invasive brown tree snake (Boiga irregularis) has been closely monitored to understand its adaptation and population control strategies (Tyrrell et al. 2009, Nafus et al. 2018).

Among all marked species, Thamnophis sirtalis was the most frequently studied, appearing in 116 references and marked using eight different techniques (cauterization, microchip, scale cutting, telemetry, natural marks, fluorescent powder, ink, and labels). Other species with over 50 studies include: Crotalus horridus (73 studies), Coluber constrictor (70 studies), Pantherophis obsoletus (68 studies), Nerodia sipedon (57 studies). These species are relatively easy to locate in their habitats, often hibernate in aggregations, and are frequently used in population monitoring studies (Brown et al. 1974, Prior & Shilton 1996, Nordberg & Cobb 2016).

Several high-density species remain understudied, despite studies documenting populations exceeding 1,000 individuals over monitoring periods of one to four years, including: Natrix tessellata (Ajtić et al. 2012), Cerberus rynchops (Chim, unpublished data), Laticauda saintgironsi (Lorioux et al. 2008, Bayrakci & Ayaz 2022). Future research should focus on these species to better understand their population dynamics and conservation needs.

Four species (being one Colubridae, one Boidae and two Viperidae) exhibited the widest variety of marking methodologies for autoecological and population studies: Coluber constrictor (11 techniques): cauterization, microchip, total scale removal, telemetry (surgery and feeding methods unspecified), elastomer, labels, tattoos, natural marks, and radioisotopes. Boa constrictor (10 techniques): microchip, telemetry (surgery, feeding, external fixation), scale removal (partial and total), elastomer, fluorescent powder, natural marks, and spool tracking. Crotalus horridus (10 techniques): cauterization, microchip, total scale removal, telemetry (surgery, ingested, external fixation), natural marks, paint, and labels. Sistrurus catenatus (10 techniques): cauterization, microchip, total scale removal, telemetry (feeding, surgery, external fixation, subdermal point), natural marks, ink, and labels. Notably, the most frequently studied species, Thamnophis sirtalis, was marked using nine different methods (see Table SI). These findings underscore the adaptability of marking techniques across species and the importance of selecting appropriate methods based on ecological traits and research objectives.

An analysis of the timeline of snake marking studies, spanning from 1933 to 2024, reveals a consistent use of various marking methods. Among them, scale cutting, telemetry, cauterization, natural marking, microchipping, and painting were the most frequently employed techniques. Notably, the use of these six techniques has increased significantly since the 2000s (see table III). This surge in research activity may be attributed to several factors: The rise of the internet and digital publishing: The widespread adoption of online scientific journals has facilitated greater accessibility to research findings and increased publication rates (Bomfá & Castro 2004); Technological advancements: Innovations such as miniaturized radio transmitters have expanded the possibilities for ecological research; Increased financial investment in ecological studies: Funding for research has improved study conditions, enabling long-term monitoring programs; and a shift in ecological research paradigms: Until the early 1990s, ecological studies on snakes were relatively rare. However, research efforts increased considerably thereafter, leading to the recognition of snakes as model organisms for ecological studies (Shine & Bonnet 2000, Luiselli 2006).

While some marking methods have become widely adopted, others have been used infrequently or have fallen out of use in the last decade. One example was the marks using iron. This technique was used between the 1970s and 2010, but only 19 studies employed it. Its decline may be due to the logistical challenges of fieldwork, including the availability of liquid nitrogen and other cooling agents, the rapid sublimation of dry ice, making long-term field use impractical or the delayed visibility of markings, requiring extended handling time (Hadow 1972, Lewke & Stroud 1974, Winne et al. 2006). Other methods that have disappeared are the use of radioisotope, tattooing and Sonic tracking. The radioisotope marking was used in only five studies between 1960 and 2010, and this method has likely been discontinued due to concerns about radioactive contamination in both the specimens and their environments (Lima et al. 2021). The tattooing technique was tested but never replicated in subsequent studies, suggesting limited effectiveness or practicality. And the sonic tracking was used exclusively in the 1980s and 1990s, being this method present in only three studies and has never been adopted anymore (see table V).

In recent years, ethical considerations and legal restrictions have also influenced the selection of marking techniques. Some countries, such as Brazil, have introduced regulations prohibiting invasive techniques that may cause harm to animals. These restrictions apply particularly to methods that involve anesthesia, surgical procedures and burning or cauterization (Tozetti & Martins 2009). As a result, researchers are increasingly shifting toward non-invasive and minimally invasive methods, such as microchipping, natural marking recognition, and telemetry, to align with ethical guidelines and animal welfare standards.

Table IV List of species with more than 1000 individuals captured in monitoring work, divided by country and climate.

Country	Climate	Species	References
Antigua e Barbuda	Tropical	Alsophis antiguae	Daltry et al. 2017
Australia	Subtropical and temperate	Acrochordus arafurae	Houston & Shine 1993, 1994, Madsen & Shine 2000, 2001, Ujvari et al. 2010
		Liasis fuscus	Madsen & Shine 1996, 1998, 1999, 2002, Madsen et al. 2006, Ujvari et al. 2015
		Stegonotus cucullatus	Brown et al. 2013, 2017
		Tropidonophis mairii	Brown et al. 2013, 2017, Brown et al. 2013
Belgium	Temperate	Vipera berus	Bauwens et al. 2018
Canada	Temperate	Crotalus oreganus	Macartney et al. 1990
		Pantherophis obsoletus	Blouin-Demers et al. 2002
		Thamnophis butleri	Skinner et al. 2024
		Thamnophis sirtalis	Gregory, unpublished data, 2011, Macmillan, unpublished data, Shine et al. 2001, 2005, 2006
Spain	Temperate	Natrix maura	Hailey & Davies 1985, 1987
United States (Guam)	Tropical	Boiga irregularis	Tyrrell et al. 2009, Nafus et al. 2018
United States	Temperate	Coluber constrictor	Brown & Parker 1976
		Crotalus horridus	Brown 2016
		Crotalus oreganus	Jenkins et al. 2009
		Crotalus tigris	Goode & Parker 2011
		Drymarchon couperi	Chandler et al. 2023
		Nerodia paucimaculata	Whiting et al. 2008
		Nerodia sipedon insularum	King et al. 2018
		Nerodia taxispilota	Mills, unpublished data
		Tantilla coronata	Todd et al. 2008
		Thamnophis atratus	Lind et al. 2005, Welsh et al. 2010
		Thamnophis elegans	Bronikowski & Arnold 1999
		Thamnophis gigas	Coates et al. 2009, Rose et al. 2018
		Thamnophis sirtalis	Rose et al. 2022
France	Temperate	Emydocephalus annulatus	Shine et al. 2020, 2021
		Laticauda colubrina	Brischoux & Bonnet 2009
		Laticauda laticaudata	Bonnet & Brischoux 2008, Brischoux & Bonnet 2008, 2009, Lorioux et al. 2008, Bonnet 2012, Fauvel et al. 2012
		Laticauda saintgironsi	Lorioux et al. 2008, Bonnet, 2012, Fauvel et al. 2012, Bonnet et al. 2014, 2015
		Vipera aspis	Bonnet et al. 1989, 2001
		Vipera ursinii	Tully et al. 2020
Italy	Temperate	Natrix tessellata	Luiselli et al. 2007
North Macedonia	Temperate	Natrix tessellata	Sterijovski 2011, 2014, Ajtic et al. 2013, Golubovic et al. 2021
Romania	Temperate	Natrix tessellata	Carlson et al. 2011
Singapore	Tropical	Cerberus rynchops	Chim 2009
Sweden	Temperate	Natrix natrix	Elmberg et al. 2024
Taiwan	Temperate	Oligodon formosanus	Lee et al. 2019
Türkiye	Temperate	Natrix tessellata	Bayrakci & Ayaz 2022

Several marking methods have emerged in recent decades, with fluorescent powder, spool tracking, and elastomer marking gaining popularity since the early 2000s (Table V). Fluorescent powder tracking is a relatively new technique used to monitor snake movements. Furman et al. (2011) first described it as a low-cost, non-invasive alternative to telemetry and spool tracking. In their study conducted in Alberta, Canada, they demonstrated the method’s efficiency for tracking snakes weighing over 10 g and with keeled scales, enabling the identification of both short and long trails, with the longest recorded at over 200 meters. This method was later replicated by Lima et al. (2021) in an Atlantic Forest environment in northeastern Brazil, where trails of up to 23 meters were recorded. The authors suggested that the technique is particularly suitable for open habitats with minimal leaf litter, such as grasslands, tundra, and Brazil’s Caatinga and Cerrado biomes. The primary advantages of fluorescent powder tracking include short-term, real-time tracking of movement patterns, low cost and ease of implementation in field studies, and to provide a complete movement path, revealing shelter sites and foraging behavior. However, it also has limitations, such as that snakes may become more vulnerable to predation when covered in fluorescent powder, and those environmental factors, such as humidity, precipitation, and substrate type, can erase or obscure tracks.

Table V
Distribution of works by each decade, differentiating the marking techniques and which countries used them. AL - Albania; AM - Armenia; AB - Antigua and Barbuda; AR - Argentina; AT - Austria; AU - Australia; BH - Bahamas; BG - Belgium; BO - Bolivia; BR - Brazil; BT - Bhutan; BU - Bulgaria; BV - Bosnia and Herzegovina; BZ - Belize; CA - Canada; CH - Chile; CM - Cameroon; CN - China; CO - Colombia; CR - Costa Rica; CU - Cuba; CY - Cyprus; CZ - Czech Republic; EN- England; EQ - Ecuador; ES - Spain; FJ - Fiji; FR - France; GD - Granada; GE - Germany; GR - Greece; HN - Honduras; HU - Hungary; IC - Ivory Coast; ID - Indonesia; IN - India; IR - Iran; IS - Israel; IT - Italy; JM - Jamaica; JP - Japan; JS - Jersey; LT - Latvia; MN - North Macedonia; MT - Montenegro; MX - Mexico; MY - Malaysia; NC - Nicaragua; NG - Nigeria; NK - North Korea; NL - Netherlands; NP - Nepal; NW - Norway; PA - Panama; PE - Peru; PG - Papua New Guinea; PO - Poland; PR - Puerto Rico; PT - Portugal; QK - Kenya; RD - Round; RO - Romania; SA - South Africa; SE - Sweden; SG - Singapore; SK - South Korea; SL - Saint Lucia Island; SR - Serbian Republic; SW - Switzerland; TC - Turks and Caicos Islands; TH - Thailand; TR - Türkiye; TW - Taiwan; UK - Ukraine; US - United States; VB - British Virgin Islands; VZ - Venezuela; WL - Wales.

Decade	Papers	Country
Telemetry (1960-2024)
1960	1	FR
1970	16	AU; BZ; CA; CR; PA; PE; US
1980	27	AU; CA; FR; SE; US
1990	56	AU; BR; CA; CR; AS; ES; GD; GE; GR; IT; MY; SE; US
2000	181	AB; AM; AU; BR; CA; CH; CM; CN; EN; ES; FR; HN; IT; JP; MX; NC; NG; PR; PT; SG; SW; TH; US; VZ
2010	243	AB; AM; AU; BG; ES; GE; BO; BR; CA; CN; CR; CZ; EN; FR; IN; IT; JM; JP; PO; PR; NK; AS; SE; SK; SW; TH; US; VZ
2020	124	AU; BR; CA; CR; HU; IN; ID; JP; MY; PE; PR; TH; TR; AS; SK; TC; US
Telemetry (Ingestion)
1960	1	FR
1970	12	AU; CA; PA; US
1980	9	AU; CA; US
1990	2	ES; SE
2000	3	AT; CH; VZ
2010	5	PO; US
2020	1	PE
Telemetry (Surgery)
1970	5	AU; BZ; CR; PE; US
1980	24	AU; CA; FR; SE; US
1990	46	AU; BR; GE; CA; CR; EM; GD; GR; MY; US
2000	160	AB; AM; AU; CA; CM; CN; EN; ES; HN; IT; JP; NG; PR; PT; SG; SW; TH; US
2010	223	AB; AM; AU; BO; BR; CA; CR; CZ; ES; FR; GE; IN; IT; JM; JP; NK; PR; AS; SW; TH; US; VZ
2020	100	AU; BR; CA; HU; ID; IN; JP; PE; PR; AS; TC; TH; TR; US
Telemetry (Externally attached radio-transmitters)
1990	3	EM; IT
2000	10	BR; NC; IT; MX; US
2010	21	BG; BR; CA; EN; PO; SA; SE; US
2020	17	BR; JP; MY; PE; SK; US
Telemetry (Bio-Loggin)
2000	1	FR
2010	4	AU; FR; US
2020	2	JP
Telemetry (Subdermal stitch)
1990	2	IT
2000	3	IT; NC
2010	3	AU; CA; SK
2020	3	AU; CA; PE
Telemetry (The method of fixation is not described)
1990	4	CA; US
2000	9	CA; IT; US
2010	14	AU; BR; US
2020	7	AU; CA; CR; PR; US
Ultrasonic pressure transmitters (1986-1998)
1980	2	PA
1990	1	AU
Radioisotopes (1969-2012)
1960	2	US
1980	2	US
2010	1	FR
Fluorescent powdered pigments (2011-2021)
2010	1	CA
2020	1	BR
Thread bobbins (2006-2023)
2000	5	BR; MX
2010	1	PE
2020	7	BR; MX; US
Microchip (1988-2024)
1980	1	US
1990	34	AU; CA; EN; FR; GR; TH; US
2000	154	AB; AM; AR; AU; BR; CA; CU; EN; FR; GD; HN; IC; JP; MX; PA; PG; PR; QN; RD, SG; SW; TH; TW; US
2010	211	AB; AM; AU; BL; BR; CA; CH; CR; EN; EQ; ES; FR; HN; HU; JM; JP; LT; MX; NG; NK; NL; PA; PR; RO; SG; SK; SL; TC; TW; US; VB
2020	100	AU; BR; CA; CH; CN; CR; CZ; EN; FR; GD; GE; HU; ID; IT; NL; MX; PA; PR; PT; TC; TH; TR; UK; US; WL
Microchip (Signal Extender Antenna)
2010	3	US
2020	1	US
Scale clipping (1881-2024)
1930	2	US
1940	4	SE; US
1950	3	US
1960	8	CA; US
1970	19	BZ; CA; EN; JP; US
1980	35	CA; EG; ES; FR; NL; SE; US
1990	83	AU; GE; BH; BR; CA; CR; FR; GD; GR; IN; IT; JP; NG; SE; US
2000	166	AU; AR; AT; BZ; BR; CA; EN; FJ; FR; IT; JP; MN; NG; PA; PO; PT; QN; SG; SE; US; VZ
2010	139	AU; BR; BH; BV; CA; CR; CU; CY; EN; ES; EQ; FR; HU; IN; IT; JM; JP; MN; MX; NG; PA; PO; RO; SA; SE; SK; SR; US; VZ
2020	51	AL; AU; AT; BR; CA; CR; CZ; ES; FR; HU; IT; JP; LT; MN; MT; MX; NP; PO; RO; RS; SE; SK; SR; SW; TH; US; VZ
Partial scale removal
1980	3	SE; FR
1990	3	IT; US
2000	1	US
2020	10	BR
Fluorescent elastomer (2007-2022)
2000	5	US
2010	1	BR
2020	11	BR; US; WL
Electric tattooing (1948)
1940	1	US
Freeze or heat branding (1971-2012)
1970	2	US
1980	1	US
1990	5	AU; US
2000	9	AU; CA; FR; US
2010	3	AU; FR
Cauterization (1969-2023)
1960	1	CA
1980	4	AU; CA; SE
1990	4	CA; SE
2000	21	BR; CA; US
2010	73	BR; CA; CR; FR; MN; SR; TH; US
2020	16	CA; CO; FR; ID; MN; TH; US
Natural marks (1946-2023)
1940	1	SE
1970	2	EN; JP
1980	10	BR; CA; ES; EN; SE; US
1990	13	AR; AU; GE; CA; EN; FR; IN; SE; US
2000	34	AT; AU; GE; BG; BR; BZ; CA; EN; GE; HU; IC; IS; MT; NL; PO; SW; TW; US; VZ
2010	51	AU; BG; BR; BU; CA; EN; ES; GE; IR; IN; IS; IT; JS; LT; US
2020	49	AU; BG; BH; BR; BT; BU; CN; EN; ES; FR; GR; HU; IN; IT; IS; JP; MX; NL; PO; SE; SW; TH; US; WL
Paint (1960-2023)
1960	2	US
1970	2	US
1980	6	AU; FR; SE; US
1990	19	CA; FR; GD; GR; IT; SE; US
2000	47	AU; AT; CA; CN; FR; IS; IT; JP; NG; PA; PT; SG; US
2010	38	AU; BR; BU; CA; FR; HU; IR; IT; JP; MX; PT; SE; SG; US
2020	26	BU; CA; ES; GD; IS; IT; NL; MX; NW; US
Tag (1962-2017)
1960	2	US
1970	3	CA; US
1980	6	ML; US
1990	4	AU; ML; US
2000	4	AU; CA; US
2010	1	CA

Spool tracking, commonly used since the mid-2000s (2006–2023), offers a more precise alternative to telemetry, as it records the actual distance traveled rather than point-to-point movement estimates (Tozetti & Martins 2009, Waddell et al. 2016, Silva et al. 2020). The main benefits of spool tracking include more accurate displacement data compared to telemetry, lower cost than radio telemetry, and effective attachment to species with keeled scales (Tozetti & Martins 2007). However, spool tracking has notable drawbacks, such as the device can get entangled in vegetation, potentially affecting movement, equipment loss is a possibility in natural environments, it is not suitable for small-bodied species, as weight can be a limiting factor (Tozetti & Martins 2007, Furman et al. 2011, Silva et al. 2020).

Elastomer marking has been increasingly used as an alternative to traditional marking methods. Unlike spool tracking and telemetry, it does not require an external device to be attached to the snake’s body, reducing interference with natural behavior and predation risk (Major et al. 2020, Barbosa et al. 2022b). Advantages of elastomer marking are that this method is minimally invasive and does not leave scars when applied with partial scale removal or on dorsal scales, it is effective for all snake sizes, including small species such as Typhlopidae, unlike tags, cauterization, and microchipping (Troast et al. 2022), the long-term durability, with recapture records exceeding three years (unpublished personal data), and the customizable color coding, allowing for unique identification (Amaral et al. 2022). A potential drawback is that not all elastomer colors are equally effective. Amaral et al. (2022) found that green polymer is less efficient than other colors, highlighting the need for further research into long-term visibility of different color variations.

Radio telemetry, first introduced in the 1970s (Fitch & Shire 1971), remains one of the most widely used techniques for active snake tracking (Duffus et al. 2024). The method involves surgically implanting a subcutaneous transmitter, enabling researchers to track movements over extended periods. As an invasive procedure, radio telemetry carries inherent risks, including surgery- and infection-mediated mortality, particularly in species sensitive to handling, and requires trained professionals to ensure safe implantation (Rudolph et al. 1998). Beyond ecological studies, radio telemetry is also used for conservation and invasive species management. For example, in “the Judas technique”, Python bivittatus individuals are equipped with radio transmitters to locate conspecifics during social behaviors, such as mating aggregations, aiding in the control of invasive populations (Harvey et al. 2008, Smith et al. 2016).

Some studies have experimented with externally attached radio transmitters as a less invasive alternative to surgical implantation. Advantages over surgery-based telemetry are lower risk of mortality and infections, suitable for smaller, slender-bodied species that would not tolerate implantation (Madrid-Sotelo & García-Aguayo 2008), easier transmitter retrieval, reducing equipment loss, and minimal behavioral disruption, with snakes resuming normal activity shortly after handling (Tozetti & Martins 2009). External transmitters were successfully attached to the rattles of Eastern Diamondback Rattlesnakes (Crotalus adamanteus), proving to be highly efficient for long-term monitoring, and non-invasive, causing no apparent harm to individuals (Jungen et al. 2019).

Despite the advantages of externally attached radio transmitters, this method presents certain challenges, particularly a higher probability of device loss. Ecdysis, ribbon detachment, and entanglement in habitat structures (e.g., rock crevices) are major factors influencing transmitter retention (Tozetti & Martins 2007, Smith et al. 2017, Park et al. 2022). Additionally, proper positioning of the transmitter and antenna size is crucial to ensure a strong and reliable signal (Madrid-Sotelo & García-Aguayo 2008). Among these factors, ecdysis is the primary limitation for short-term monitoring, as snakes shed their skin periodically, leading to the premature loss of transmitters (Madrid-Sotelo & García-Aguayo 2008, Tozetti & Martins 2009). However, Madrid-Sotelo & García-Aguayo (2008) reported no skin lesions in Oxybelis aeneus after using non-oily acetone to remove tape-based attachments at the end of their study. Alternative attachment methods include glue and tape combinations, which have been successfully used without recorded injuries (Robinson et al. 2018). However, other attachment methods have reported adverse effects such as the glue or silver tape may cause skin irritation, injuries, and infections (Riley et al. 2017, Robinson et al. 2018), and the nylon thread and epoxy resin can lead to lacerations on the snake’s body (Park et al. 2022). To mitigate these risks, subdermal attachment techniques have been proposed as a less invasive alternative to surgical implantation, offering better transmitter retention than glue, thread, or tape while avoiding infections over the study period (Riley et al. 2017, Wolfe et al. 2018). Ultimately, a species-specific assessment of morphology and habitat is essential when selecting the most appropriate attachment method.

Beyond traditional radio telemetry, some researchers have explored acoustic telemetry for tracking marine snake species, such as Acrochordus arafurae, Hydrophis curtus, and Hydrophis elegans (Pratt et al. 2010, Udyawer et al. 2015a, 2015b, 2017). These studies utilized V9P-2H coded acoustic transmitters (Vemco), which, unlike conventional radio transmitters, provide not only location data but also dive depth, allowing for a three-dimensional analysis of habitat use (Udyawer et al. 2017). Another recent innovation in telemetry is the integration of Bio-Logging GPS technology with radio transmitters, however, this approach also presents limitations, including high costs, restricted battery life, potential impacts on animal behavior, and reduced signal reliability in certain environments such as underground or structurally complex habitats. This technique, first implemented in the early 2000s, provides precise data on home range and movement patterns (Brischoux et al. 2007, Smith et al. 2018, Wolfe et al. 2018), making it one of the most advanced telemetry methods available today.

Ink-based marking techniques have been widely used for individual snake identification, employing various materials such as codes, figures, or numbers. Several studies have tested different quick-drying, non-toxic paints, including Paintstik® industrial chalk – Used for marking Nerodia sipedon insularium (King et al. 2018); Ultraviolet ink – Applied to Cerastes cerastes for invisible markings visible under UV light (Subach et al. 2021); Nail polish – Tested for marking snakes in short-term studies (Dalessi et al. 2020); Leather paint – Used for marking Vipera berus (Madsen & Ujvari 2011); Sanford Magnum 44® permanent marker – Applied to Gloydius shedaoensis (Shine & Li-Xin 2002); Fine-point Sanford “Sharpie” – Used on Corallus grenadensis (Henderson et al. 1998); Acrylic paint – Tested on Nerodia sipedon (Brown & Weatherhead 2004); Quick-drying waterproof paint – Applied to Crotalus atrox, C. molossus, and C. scutulatus (Pough 1966) and Echis coloratus (Tsairi & Bouskila 2004). These marking techniques offer simple, cost-effective alternatives for short-term studies, but their durability and visibility may vary depending on species, habitat, and environmental conditions.

Studies utilizing natural marks for individual recognition have primarily relied on photographs and/or drawings analyzed manually by researchers (Hailey & Davies 1985, Benson 1999, Bentes et al. 2017) from the 1990s to the present. However, over the past decade, researchers have increasingly employed specialized software to compare images of captured and recaptured specimens based on the arrangement and shape of their scales. These technological advancements have significantly reduced the time required for image verification while maintaining high reliability in species identification (Hoefer et al. 2021, Lukanov & Dyugmedzhiev 2023). Additionally, Imlay et al. (2015) reported individual recognition in Thamnophis saurita through patterns in their ecdysis.

For marking studies that employed labels, various materials have been used. Examples include autoclave tape with numerical markings affixed to the head of Thamnophis sirtalis (Heller & Halpern 1982) and “Identi-Tape” (reflective tape) secured with surgical glue on the irregularly shaped body of Boiga species (Rodda et al. 2007). The “Monel self-piercing tag” was attached to the corner of the mouth in Thamnophis elegans (Thomas & Eklund 1962), Coluber constrictor, and Masticophis taeniatus taeniatus (Hirth 1966). While Thomas & Eklund (1962) recommended this method for long-term studies, it was not replicated after Hirth (1966). Voris (1985) tested the use of “Monel self-piercing tag” on the tail of Hydrophis schistosus, as well as “Floy® T-Bar Anchor Fish” and “Swiftach® Systems.” However, Burns & Heatwole (2000), who initially tagged Aipysurus laevis in the same way, later abandoned this method in favor of branding and scale cutting. Their decision was influenced by the failure to recapture tagged individuals after one year and frequent observations of snakes with missing tails, likely due to predation by larger fish mistaking the tags for prey.

Among the various marking techniques, microchipping has remained one of the most widely used worldwide. It is considered a highly reliable method, particularly for medium to large snake species, and has proven effective for both short- and long-term monitoring. Some marked individuals have been successfully recaptured more than 30 years after implantation (Burger et al. 2018). However, studies by Roark & Dorcas (2000) on Pantherophis guttatus highlighted potential drawbacks, such as the expulsion of microchips via the intestinal tract or their absorption within the body. These findings indicate the need for further research to assess the frequency and impact of microchip loss in wild populations. Nevertheless, microchipping remains one of the preferred methods for mark-recapture studies due to its durability and accuracy.

Australia, Mexico, and Brazil harbor the greatest reptile diversity worldwide (Costa et al. 2022). Regarding snakes, Brazil has the highest species richness, with 435 described species (Guedes et al. 2023), followed by Mexico (454 species) and Australia (228 species). The United States, with 225 snake species, is also among the most species-rich countries (Uetz et al. 2025). Notably, over 50% of the snake species studied using marking methods were from the United States. However, despite a lower number of studies in Brazil compared to the U.S., Brazil exhibited the greatest species richness among studied taxa. This outcome likely reflects the comprehensive inventories and surveys conducted across diverse Brazilian ecosystems, encompassing both abundant and rare species (França & Braz 2013, Sampaio et al. 2018, Barbosa et al. 2022b). In contrast, many U.S. studies focus on a single species, particularly those that hibernate in aggregations and are locally abundant (Wood et al. 2020, Duffus et al. 2022, Rose et al. 2022). There remains substantial potential for expanding mark-recapture research, particularly in Mexico, where fewer than 5% of native species have been studied using these methodologies.

CONCLUSIONS

The advancement of snake marking techniques has substantially enhanced ecological research by enabling individual identification, movement tracking, and population monitoring. This review highlights the widespread use of multiple approaches, with radio telemetry, scale clipping, microchipping, and natural markings being the most commonly applied methods. Each technique presents clear trade-offs: telemetry is highly effective for movement and survival estimates but is invasive; permanent marks such as scale clipping and cauterization ensure long-term identification but involve physical alteration; while non-invasive methods, including paints and fluorescent markers, offer low-cost alternatives but are generally limited in durability.

Method choice varied primarily according to research objectives, species biology, and logistical constraints, rather than geographic preference, suggesting broad methodological consistency across regions. Recent innovations, such as elastomer marking and fluorescent powder, expand the methodological toolkit by offering less invasive and more flexible options. Future research should prioritize refining these techniques, integrating emerging technologies, and improving ethical standards to minimize impacts on animal welfare. Such advances will strengthen long-term ecological studies and support more effective conservation and management strategies for snake populations worldwide.

SUPPLEMENTARY MATERIAL

Appendix S1. Figures S1-S7. Table SI.

Appendix S1. Figures S1-S7. Table SI.

Acknowledgements

We would like to thank Tarcísio Silva for creating the images of the snakes used in the family graphic. VNB thanks the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for PhD scholarship (grant number 88887.713778/2022-00).

• Data availability
  The data supporting the findings of this study are available within the article and its Supplementary Material.

References

• AJTIĆ R ET AL. 2012. Unexpected life history traits in a very dense population of dice snakes. Zool Anz 252: 350-358.
• ALBERTS A. 2006. Conserving the remarkable reptiles of Guantánamo Bay. Iguana 13: 8-15.
• ALEXANDER GJ & MARITZ B. 2015. Sampling interval affects the estimation of movement parameters in four species of African snakes. J Zool 297: 309-318.
• ALLENDER MC, HILEMAN ET, MOORE J & TETZLAFF S. 2016. Detection of Ophidiomyces, the Causative Agent of Snake Fungal Disease, in the Eastern Massasauga (Sistrurus catenatus) in Michigan, USA, 2014. J Wildl Dis 52: 694-698.
• AMARAL JMS, BARBOSA VN & FRANÇA FGR. 2022. Use of visible fluorescent elastomer to monitor Chironius flavolineatus (Serpentes: Colubridae) in the Atlantic Forest. Nat Conserv 15: 53-59.
• AMIEL J & WASSERSUG R. 2010. Temperature differentials between the bodies and tails of ribbon snakes (Thamnophis sauritus): ecological and physiological implications. Amphib Reptil 31: 257-263.
• ANGARITA-SIERRA T & LÓPEZ-HURTADO C. A. 2020. Exploring the reproductive ecology of the tropical semifossorial snake Ninia atrata Zool Res 41: 157-171.
• BAIER F & WIEDL HJ. 2010. The re-evaluated conservation status of the mountain populations of the highly endangered Cyprus grass snake, Natrix natrix cypriaca (Hecht, 1930), with miscellaneous natural history notes. Salamandra 46: 16-23.
• BARBOSA VDN, AMARAL JMS, GUSMÃO RAF, LIMA LFL, SOUZA JVM, AGUIAR IDS & SANTOS EMD. 2020a. Serpentes de uma área de proteção urbana da Floresta Atlântica nordestina brasileira. Cuad Herpetol 34: 201-209.
• BARBOSA VDN, DA SILVA AMARAL JM, SANTOS SSD & FRANÇA FGR. 2022. Predation on the common marmoset Callithrix jacchus (Primates, Callitrichidae) by the common boa Boa constrictor (Squamata, Boidae) in the Atlantic Forest of Northeastern Brazil. Bol Mus Para Emílio Goeldi 17: 251-255.
• BARBOSA VN, AMARAL JMS & FRANÇA FGR. 2022b. Snake diversity of the Barra do Rio Mamanguape environmental protection area in Northeast Brazil. Rev Ibero-Am Ciênc Ambient 13: 84-97.
• BASAVARAJU Y, DEVI BSR, MUKHATYAKKA G, REDDY LP, MAIR GC, RODERICK EE & PENMAN DJ. 1998. Evaluation of marking and tagging methods for genetic studies in carp. J Biosci 23: 585-593.
• BAYRAKCI Y & AYAZ D. 2022. Dynamics of a Western Anatolian population of Natrix natrix and Natrix tessellata (Serpentes: Natricidae). Turk J Zool 46: 270-277.
• BENSON PA. 1999. Identifying individual adders, Vipera berus, within an isolated colony in east Yorkshire. Bulletin-British Herpetological Society (67): 21-27.
• BENTES AP, BENTES SS & SANTOS-JR AP. 2017. Utilização de marcas naturais para individualização da Cobra-d’água Helicops polylepis Gunther, 1861 (Dipsadidae, Xenodontinae). Biota Amazôn 7: 69-73.
• BLANCHARD FN & FINSTER EB. 1933. A Method of Marking Living Snakes for Future Recognition, with a Discussion of Some Problems and Results. Ecology 14: 334-347.
• BOMFÁ CRZ & CASTRO JEE. 2004. Desenvolvimento de revistas científicas em mídia digital: o caso da Revista Produção Online. Ci Inf 33: 39-48.
• BONNET X. 2012. Long-term field study of sea kraits in New Caledonia: fundamental issues and conservation. ICB 52: 281-295.
• BONNET X & BRISCHOUX F. 2008. Thirsty sea snakes forsake refuge during rainfall. Austral Ecol 33: 911-921.
• BONNET X, NAULLEAU G & LOURDAIS O. 1989. Benefits of complementary techniques: using capture-recapture and physiological approaches to understand costs of reproduction in the aspic viper (Vipera aspis). In: Schuett GW et al. (Eds), Biology of the Vipers, Utah: Eagle Mountain Pub Lc, Eagle Mountain, USA, p. 483-495.
• BONNET X, NAULLEAU G, SHINE R & LOURDAIS O. 2001. Short-term versus long-term effects of food intake on reproductive output in a viviparous snake, Vipera aspis Oikos 92: 297-308.
• BONNET X, BRISCHOUX F, BONNET C, PLICHON P & FAUVEL T. 2014. Coastal nurseries and their importance for conservation of sea kraits. PLoS ONE 9: e90246.
• BONNET X, BRISCHOUX F, PINAUD D, MICHEL CL, CLOBERT J, SHINE R & FAUVEL T. 2015. Spatial variation in age structure among colonies of a marine snake: the influence of ectothermy. J Anim Ecol 84: 925-933.
• BOUNDY J. 2020. Snakes of the World: a supplement. Boca Raton, Florida, EUA: CRC Press, 282 p.
• BOVO RP, MARQUES OAV & ANDRADE DV. 2012. When basking is not an option: thermoregulation of a Viperid snake endemic to a small island in the south Atlantic of Brazil. Copeia 2012: 408-418.
• BRISCHOUX F & BONNET X. 2008. Estimating the impact of sea kraits on the Anguilliform fish community (Congridae, Muraenidae, Ophichthidae) of New Caledonia. Aquat Living Resour 21: 395-399.
• BRISCHOUX F & BONNET X. 2009. Life history of sea kraits in New Caledonia. In: Grandcolas P (Ed), Zoologia neocaledonica 7. Biodiversity studies in New Caledonia, New Caledonia: Muséum National d’Histoire Naturelle, Paris, France, p. 133-147.
• BRISCHOUX F, BONNET X & SHINE R. 2007. Foraging ecology of sea kraits Laticauda spp. in the Neo-Caledonian Lagoon. Mar Ecol Prog Ser 350: 145-151.
• BROWN GP, MADSEN T & SHINE R. 2017. Resource availability and sexual size dimorphism: differential effects of prey abundance on the growth rates of tropical snakes. Funct Ecol 31: 1592-1599.
• BROWN GP & SHINE R. 2006. Why do most tropical animals reproduce seasonally? testing hypotheses on an australian snake. Ecology 87: 133-143.
• BROWN GP, UJVARI B, MADSEN T & SHINE R. 2013. Invader impact clarifies the roles of top-down and bottom-up effects on tropical snake populations. Funct Ecol 27: 351-361.
• BROWN WS. 2016. Lifetime Reproduction in a Northern Metapopulation of Timber Rattlesnakes (Crotalus horridus). Herpetologica 72: 331-342.
• BROWN WS & PARKER WS. 1976. A Ventral scale clipping system for permanently marking snakes (Reptilia, Serpentes). J Herpetol 10: 247.
• BROWN WS, PARKER WS & ELDER JA. 1974. Thermal and spatial relationships of two species of Colubrid snakes during hibernation. Herpetologic 30: 32-38.
• BROWN GP & WEATHERHEAD PJ. 2004. Sexual abstinence and the cost of reproduction in adult male water snakes, Nerodia sipedon Oikos 104: 269-276.
• BURGER J, ZAPPALORTI RT & GOCHFELD M. 2018. Hatchling survival to breeding age in Northern Pine Snakes (Pituophis melanoleucus) in the New Jersey Pine Barrens: Human effects on recruitment from 1986 to 2017. PLoS ONE 13: e0195676.
• BURNS G & HEATWOLE H. 2000. Growth, sexual dimorphism, and population biology of the olive sea snake, Aipysurus laevis, on the Great Barrier Reef of Australia. Amphib-Reptil 21: 289-300.
• CAPULA M, LUISELLI L, VALENTI S, CECCARELLI A, RUGIERO L & ALOISE G. 2006. Are endemic snakes with a narrow distribution more specialist than their wide-ranging counterparts? Evidence from the prey composition and morphometric correlates of the diet in Zamenis lineatus, a rat snake endemic to southern Italy. Amphib-Reptil 27: 531-537.
• CARTER ET, RAVESI MJ, EADS BC & KINGSBURY BA. 2017. Invasive plant management creates ecological traps for snakes. Biol Invasions 19: 443-453.
• CHAMPAGNE PS. 2022. Conservation ecology of Eunectes murinus (green anaconda) in the madre de dios region of southeastern Peru using remote sensing techniques and machine learning driven geospatial modeling. Master of Science, Acadia University, Wolfville, Canadá. (Unpublished).
• CIOFI C & CHELAZZI G. 1991. Radiotracking of Coluber viridiflavus Using External Transmitters. J Herpetol 25: 37-40.
• CLARK DR. 1971. Branding as a marking technique for amphibians and reptiles. Copeia 1971: 148-151.
• COATES PS, WYLIE GD, HALSTEAD BJ & CASAZZA ML. 2009. Using time-dependent models to investigate body condition and growth rate of the giant gartersnake. J Zool 279: 285-293.
• COBB VA, GREEN JJ, WORRALL T, PRUETT J & GLORIOSO B. 2005. Initial Den Location Behavior in a Litter of Neonate Crotalus horridus (Timber Rattlesnakes). SENA 4: 723-730.
• COLBERT JE, ANDREWS KM & NORTON TM. 2014. Agkistrodon piscivorus (cottonmouth). Diet and prey size. Herpetol Rev 45: 703-704.
• COSTA HC, GUEDES TB & BÉRNILS RS. 2022. 2022. Lista de répteis do Brasil: padrões e tendências. Herpetologia Brasileira 10: 110-279.
• DALESSI D, BOLLE H, JONGEJANS E, SØRENSEN P & SIEPEL H. 2020. Reproduction probabilities and size distributions of the smooth snake Coronella austriaca in the Netherlands and Norway. Amphib-Reptil 42: 167-178.
• DALRYMPLE GH & REICHENBACH NG. 1981. Interactions between the prairie garter snake (Thamnophis radix) and the common garter snake (T. sirtalis) in Killdeer Plains, Wyandot County, Ohio. Ohio Biol Surv Biol Notes 15: 244-250.
• DALTRY JC, LINDSAY K, LAWRENCE SN, MORTON MN, OTTO A & THIBOU A. 2017. Successful reintroduction of the Critically Endangered Antiguan racer Alsophis antiguae to offshore islands in Antigua, West Indies. Int Zoo Yearb 51: 97-106.
• DIAZ FR & BLOUIN-DEMERS G. 2017. Northern Snakes Appear Much More Abundant in Old Fields than in Forests. Can Field-Nat 131: 228-234.
• DUFFUS A, TIPTON AF, THOMPSON M, TILLETT W, POWERS J, BARTLETT D & DESANTIS D. 2024. Ophidiomycosis in a Timber Rattlesnake, Crotalus horridus (Linnaeus 1758), with behavioral and thermal observations: A case report from Georgia, USA. Reptiles & Amphibians 31: e21443.
• DUFFUS ALJ, HUGHES DF, KAUTZ A, ALLAIN SJR & MESHAKA WE. 2022. Repeated sampling of wild individuals reveals ophidiomyces ophidiicola infection dynamics in a Pennsylvania snake assemblage. J Wildl Dis 58: 290-297.
• DYUGMEDZHIEV AV, NAUMOV BY & TZANKOV ND. 2023. Interpopulation Variations in Circadian Activity of the Nose-horned Viper Vipera ammodytes (Linnaeus, 1758) (Reptilia: Viperidae). Acta Zool Bulg 75: 67-73.
• ELMBERG J, PALMHEDEN L, EDELSTAM C, HAGMAN M & KÄRVEMO S. 2024. Climate change-induced shifts in survival and size of the worlds’ northernmost oviparous snake: A 68-year study. PLoS ONE 19: e0300363.
• ERNST CH, ORR JM, CREQUE TR, LAEMMERZAHL AF & HARTSELL TD. 2012. Annual and daily activity cycles of snakes in northern Virginia, USA. Herpetological Bulletin 121: 23-28.
• FAUVEL T, BRISCHOUX F, BRIAND MJ & BONNET X. 2012. Do researchers impact their study populations? Assessing the effect of field procedures in a long term population monitoring of sea kraits. Amphib-Reptil 33: 365-372.
• FITCH HS. 1960. Autecology of the Copperhead. Univ. Kans publ Mus Nat Hist 13: 85-228.
• FITCH HS. 1987. Collecting and life history techniques. In: Seigel RA, Collins JT & Novak SS (Eds), Snakes: Ecology and evolutionary Biology, New York: MacMillan Publi. Co., New York, USA, p. 143-164.
• FITCH HS & SHIRER HW. 1971. A radiotelemetric study of spatial relationships in some common snakes. Copeia 1971: 118-128.
• FRANÇA FGR & BRAZ VS. 2013. Diversity, activity patterns, and habitat use of the snake fauna of Chapada dos Veadeiros National Park in Central Brazil. Biota Neotrop 13: 74-84.
• FURMAN BLS, SCHEFFERS BR & PASZKOWSKI CA. 2011. The use of fluorescent powdered pigments as a tracking technique for snakes. Herpetol Conserv Biol 6: 473-478.
• GENT AH & SPELLERBERG IF. 1993. Movement rates of the smooth snake Coronella austriaca (Colubridae) A radio telemetric study. J Herpetol 3: 140-146.
• GERKE HC, HINTON TG & BEASLEY JC. 2021. Movement Behavior and Habitat Selection of Rat Snakes (Elaphe spp.) in the Fukushima Exclusion Zone. Ichthyol Herpetol 109: 545-556.
• GIBBONS JW & ANDREWS KM. 2004. PIT Tagging: Simple technology at its best. BioScience 54: 447-454.
• GOETZ SM, HILEMAN ET, NAFUS MG, ADAMS AAY, BRYANT AR, REED RN & SIERS SR. 2021. Brown Treesnake Mortality After Aerial Application of Toxic Baits. J Wildl Manage 85: 1507-1514.
• GOLUBOVIĆ A, ANĐELKOVIĆ M, TOMOVIĆ L, ARSOVSKI D, GVOZDENOVIĆ S, ŠUKALO G, AJTIĆ R & BONNET X. 2021. Death-feigning propensity varies within dice snake populations but not with sex or colour morph. J Zool 314: 203-210.
• GOODE M & PARKER MR. 2011. Microgeographic variation in Tiger rattlesnake ecology and life History. Reptiles & Amphibians 18: 84-91.
• GRAY BS. 2013. Aggregations of brownsnakes, Storeria dekayi (Holbrook, 1836), at a Site in Northwestern Pennsylvania. Bull Chic Herpetol Soc Bull 48: 33-38.
• GREENE HW. 1997. Snakes: the evolution of mystery in nature, 45th ed., California: Univ of California Press, 366 p.
• GREENE HW, MAY PG, HARDY SR, SCITURRO JM & FARRELL TM. 2002. Parental behavior by vipers. In: Schuett GW et al. (Eds), Biology of the Vipers, Utah: Eagle Mountain Pub Lc, Eagle Mountain, USA, p. 179-205.
• GREGORY PT. 2011. Temporal dynamics of relative-mass variation of red-sided garter snakes (Thamnophis sirtalis parietalis) at a communal hibernaculum in Manitoba. Ecoscience 18: 1-8.
• GREGORY PT, ISAAC LA & GRIFFITHS RA. 2007. Death feigning by grass snakes (Natrix natrix) in response to handling by human “predators”. J Comp Psychol 121: 123-129.
• GUEDES TB ET AL. 2017. Patterns, biases and prospects in the distribution and diversity of neotropical snakes. Glob Ecol Biogeogr 27: 14-21.
• GUEDES TB, ENTIAUSPE-NETO OM & COSTA HC. 2023. Lista de répteis do Brasil: atualização de 2022. Herpetol Bras 12: 56-161.
• HADOW HH. 1972. Freeze-Branding: a permanent marking technique for pigmented mammals. J Wildl Manage 36: 645-649.
• HAILEY A & DAVIES PMC. 1985. ‘Fingerprinting’snakes: a digital system applied to a population of Natrix maura. J Zool 207: 191-199.
• HAILEY A & DAVIES PMC. 1987. Growth, movement and population dynamics of Natrix maura in a drying river. Herpetol J 1: 185-194.
• HAMILTON MB. 2021. Population genetics, 2nd ed., New Jersey, John Wiley & Sons, New York, USA, p. 496.
• HARVEY RG, BRIEN ML, CHERKISS MS, DORCAS M, ROCHFORD M, SNOW RW & MAZZOTTI FJ. 2008. Burmese Pythons in South Florida: Scientific Support for Invasive Species Management. EDIS 2008: 1-9.
• HASKINS DL, BROWN MK, BRINGOLF RB & TUBERVILLE TD. 2021. Brown watersnakes (Nerodia taxispilota) as bioindicators of mercury contamination in a riverine system. The Science of the Total Environment 755: 142545.
• HASKINS DL, BROWN MK, MEICHNER K, COLEMAN AL, ALLENDER MC & TUBERVILLE TD. 2024. Factors predicting apparent ophidiomycosis in wild brown watersnakes (Nerodia taxispilota). J Wildl Dis 60: 64-76.
• HELLER SB & HALPERN M. 1982. Laboratory observations of aggregative behavior of garter snakes, Thamnophis sirtalis J Comp Physiol Psychol 96: 967-983.
• HENDERSON RW, SAJDAK RA & WINSTEL RA. 1998. Habitat utilization by the arboreal boa Corallus grenadensis in two ecologically disparate habitats on Grenada. Amphib-Reptil 19: 203-214.
• HIRTH HF. 1966. Changes and mortality of three species of snakes during hibernation. Herpetologica 22: 8-12.
• HIRTH HF, PENDLETON RC, KING AC & DOWNARD TR. 1969. Dispersal of Snakes from a Hibernaculum in Northerwestern Utah. Ecology 50: 332-339.
• HOEFER S, ROTGER A, MILLS S & ROBINSON NJ. 2021. Semi-automated photo-identification of bahamian racers (Cubophis vudii vudii). Acta Herpetol 16: 133-136.
• HOLDING ML, FRAZIER JA, DORR SW, HENNINGSEN SN, MOORE IT & TAYLOR EN. 2014. Physiological and behavioral effects of repeated handling and short-distance translocations on free-ranging northern pacific rattlesnakes (Crotalus oreganus oreganus). J Herpetol 48: 233-239.
• HOUSTON D & SHINE R. 1993. Sexual dimorphism and niche divergence: Feeding habits of the Arafura Filesnake. J Anim Ecol 62: 737-748.
• HOUSTON D & SHINE R. 1994. Low growth rates and delayed maturation in arafura filesnakes (Serpentes: acrochordidae) in tropical Australia. Copeia 1994: 726-731.
• HOWARTH CR, BISHOP CA & LARSEN KW. 2023. Western Rattlesnake (Crotalus oreganus) spring migration in British Columbia: a comparative study of juveniles and adults. Can J Zool 101: 530-540.
• HUNDNALL JA. 1982. New methods for measuring and tagging snakes. Herpetol Rev 13: 97-98.
• IMLAY TL, SAROLI J, HERMAN TB & MOCKFORD SW. 2015. Movements of the Eastern ribbonsnake (Thamnophis sauritus) in Nova Scotia. Can Field-Nat 129: 379-385.
• JANECKA MJ, JANECKA JE, HAINES AM, MICHAELS A & CRISCIONE CD. 2021. Post-delisting genetic monitoring reveals population subdivision along river and reservoir localities of the endemic Concho Water Snake (Nerodia harteri paucimaculata). Conservation Genetics 22: 1005-1021.
• JENKINS CL, PETERSON CR, DOERING SC & COBB VA. 2009. Microgeographic variation in reproductive characteristics among western rattlesnake (Crotalus oreganus) populations. Copeia 2009: 774-780.
• JONES PC, KING RB & SUTTON S. 2017. Demographic analysis of imperiled Eastern Massasaugas (Sistrurus catenatus catenatus). J Herpetol 51: 383-387.
• JORDAN MA, PERRINE-RIPPLINGER N & CARTER ET. 2015. An independent observation of facultative parthenogenesis in the copperhead (Agkistrodon contortrix). J Herpetol 49: 118-121.
• JUNGEN MT, ROSS Z, COOLEY J, MARTIN MD, HOLLOWAY J, WELCH SM & WALDRON JL. 2019. Monitoring eastern diamondback rattlesnakes using a novel external Radio-Transmitter attachment method. Copeia 107: 411-416.
• KIAN N, KABOLI M, KARAMI M, ALIZADEH A, TEYMURZAD EH, KHALILBEIGI N, MURPHY JB & NOURANI E. 2011. Captive management and reproductive biology of Latifi’s viper (Montivipera latifii) (Squamata: Viperidae) at Razi Institute and Tehran University in Iran. Herpetol Rev 42: 535-539.
• KING RB & LAWSON R. 1995. Color-pattern variation in lake erie water snakes: The role of gene flow. Evolution 49: 885-896.
• KING RB, STANFORD KM & JONES PC. 2018. Sunning themselves in heaps, knots, and snarls: The extraordinary abundance and demography of island watersnakes. Ecol Evol 8: 7500-7521.
• KISSNER KJ, FORBES MR & SECOY DM. 1997. Rattling Behavior of Prairie Rattlesnakes (Crotalus viridis viridis, Viperidae) in Relation to Sex, Reproductive Status, Body Size, and Body Temperature. Ethology 103: 1042-1050.
• LEE C-Y, PIKE DA, TSENG H-Y, HSU J-Y, HUANG S-L, SHANER P-JL, LIAO C-P, MANICA A & HUANG W-S. 2019. When males live longer: Resource-driven territorial behavior drives sex-specific survival in snakes. Science Advances 5: 5478-5502.
• LEE TJ, JELLEN BC, SIEGEL DS & ALDRIDGE RD. 2010. Homosexual Reproductive Behavior in the African Brown House Snake (Lamprophis fuliginosus). Reptiles & Amphibians 17: 208-209.
• LEMAIRE J, BUSTAMANTE P, OLIVIER A, LOURDAIS O, MICHAUD B, BOISSINOT A, GALÁN P & BRISCHOUX F. 2018. Determinants of mercury contamination in Viperine snakes, Natrix maura, in Western Europe. Sci Total Environ 635: 20-25.
• LEWKE RE & STROUD RK. 1974. Freeze-Branding as a method of marking snakes. Copeia 1974: 997-1000.
• LILLYWHITE HB. 1980. Behavioral thermoregulation in Australian Elapid snakes. Copeia 1980: 452-458.
• LIMA ACD, CUNHA DA, ALBUQUERQUE LC, COSTA RNA & SILVA HJ. 2018. Alterações sensoriais em respiradores orais: Revisão sistemática baseada no método prisma. RPPed 37: 97-103.
• LIMA LFL, BARBOSA VN & SANTOS EM. 2021. Uso do pó fluorescente no estudo de rastreamento de serpentes na Floresta Atlântica, Nordeste, Brasil. Cuad Herpetol 35: 273-281.
• LIND AJ, WELSH HH & TALLMON DA. 2005. Garter snake population dynamics from a 16-year study: considerations for ecological monitoring. Ecol Appl 15: 294-303.
• LORIOUX S, BONNET X, BRISCHOUX F & DE CRIGNIS M. 2008. Is melanism adaptive in sea kraits? Amphib-Reptil 29: 1-5.
• LUISELLI L. 2006. Testing hypotheses on the ecological patterns of rarity using a novel model of study: snake communities worldwide. Web Ecol 6: 44-58.
• LUISELLI L, CAPIZZI D, FILIPPI E, ANIBALDI C, RUGIERO L & CAPULA M. 2007. Comparative diets of three populations of an aquatic snake (Natrix Tessellata, Colubridae) from mediterranean streams with different hydric regimes. Copeia 2007: 426-435.
• LUISELLI L, VIGNOLI L, RUGIERO L & MEEK R. 2018. Declining occupancy rates in the hibernacula of aspic vipers (Vipera aspis) in Italy and France; evidence for climatic effects? Herpetological Journal 28: 137-142.
• LUKANOV S & DYUGMEDZHIEV A. 2023. Photo identification of viperid snakes using pattern recognition software: a case study of Vipera ammodytes (Linnaeus, 1758). North-Western J Zool 19: 41-45.
• MACARTNEY JM & GREGORY PT. 1988. Reproductive biology of female rattlesnakes (Crotalus viridis) in British Columbia. Copeia 1: 47-57.
• MACARTNEY JM, GREGORY PT & CHARLAND MB. 1990. Growth and Sexual Maturity of the Western Rattlesnake, Crotalus viridis, in British Columbia. Copeia 1990: 528-542.
• MADRID-SOTELO CA & GARCÍA-AGUAYO A. 2008. A simple method for externally attaching radio-transmitters to snakes. North-West J Zool 4: 335-338.
• MADRID-SOTELO CA & VALDIVIA CJB. 2008. Técnicas de colocación de radiotransmisores en serpientes. Bol Soc Herp Mex 16: 5-12.
• MADSEN T & SHINE R. 1996. Seasonal migration of predators and Prey--A study of pythons and rats in Tropical Australia. Ecology 77: 149-156.
• MADSEN T & SHINE R. 1998. Spatial subdivision within a population of tropical pythons (Liasis fuscus) in a superficially homogeneous habitat. Aust J Ecol 23: 340-348.
• MADSEN T & SHINE R. 1999. Life history consequences of nest-site variation in tropical pythons (Liasis fuscus). Ecology 80: 989-997.
• MADSEN T & SHINE R. 2000. Rain, fish and snakes: climatically driven population dynamics of Arafura filesnakes in tropical Australia. Oecologia 124: 208-215.
• MADSEN T & SHINE R. 2001. Conflicting conclusions from long-term versus short-term studies on growth and reproduction of a tropical snake. Herpetologica 57: 147-156.
• MADSEN T & SHINE R. 2002. Short and chubby or long and slim? Food intake, growth and body condition in free-ranging pythons. Austral Ecol 27: 672-680.
• MADSEN T & UJVARI B. 2011. The potential demise of a population of adders (Vipera berus) in Smygehuk, Sweden. Herpetol Conserv Biol 6: 72-74.
• MADSEN T, UJVARI B, SHINE R & OLSSON M. 2006. Rain, rats and pythons: Climate-driven population dynamics of predators and prey in tropical Australia. Austral Ecol 31: 30-37.
• MAJOR T, ALKINS DR, JEFFREY L & WÜSTER W. 2020. Marking the un-markable: visible implant elastomer in wild juvenile snakes. Herpetol J 30: 173-176.
• MANIER MK & ARNOLD SJ. 2005. Population genetic analysis identifies source-sink dynamics for two sympatric garter snake species (Thamnophis elegans and Thamnophis sirtalis). Mol Ecol 14: 3965-3976.
• MCKENZIE JM, PRICE SJ, CONNETTE GM, BONNER SJ & LORCH JM. 2021. Effects of snake fungal disease on short-term survival, behavior, and movement in free-ranging snakes. Ecol Appl 31: e02251. 10.1002/eap.2251.
  » https://doi.org/10.1002/eap.2251
• METCALF MF, GUNNELS IV C, WALLACE F, BROSSE W & HERMAM JE. 2020. Crotalus adamanteus (Eastern Diamond-backed Rattlesnake). Same-sex courting. Herpetol Rev 51: 344-345.
• MURRAY DL & FULLER MR. 2000. A critical review of the effects of marking on the biology of vertebrates. In: Boitani L & Fuller T (Eds), Research techniques in animal ecology: controversies and consequences, New York, Columbia University Press, New York, USA, p. 15-64.
• NAFUS MG, ADAMS AAY, BOBACK SM, SIERS SR & REED RN. 2020a. Behavior, size, and body condition predict susceptibility to management and reflect post-treatment frequency shifts in an invasive snake. Global Ecol Conserv 21: e00834.
• NAFUS MG, ADAMS AAY, KLUG PE & RODDA GH. 2018. Habitat type and structure affect trap capture success of an invasive snake across variable densities. Ecosphere 9: e02339.
• NAFUS MG, MAZZOTTI FJ & REED RN. 2020b. Estimating Detection Probability for Burmese Pythons with Few Detections and Zero Recaptures. J Herpetol 54: 24-30.
• NAFUS MG, REYES A, FIES T & GOETZ SM. 2024. Adaptive resource management: Achieving functional eradication of invasive snakes to benefit avian conservation. J Appl Ecol 61: 733-745.
• NANNI GESER S & URSENBACHER S. 2022. Multiple paternity in the Asp viper. J Zool 318: 158-165.
• NGUYEN AM, TODD BD & HALSTEAD BJ. 2023. Survival and establishment of captive-reared and translocated giant gartersnakes after release. J Wildl Manage 87: e22374.
• NORDBERG EJ & COBB VA. 2016. Midwinter emergence in hibernating timber rattlesnakes (Crotalus horridus). J Herpetol 50: 203-208.
• OLDHAM CR, FLECKENSTEIN III JL, BOYS WA & PRICE SJ. 2016. Enhancing ecological investigations of snakes with passive integrated transponder (PIT) tag telemetry. Herpetol Rev 47: 385-388.
• OLDHAM CR, PRICE SJ, BOYS WA & FLECKENSTEIN III LJ. 2015. Regina septemvittata (Queensnake). Defensive behavior/death-feigning. Herpetol Rev 46: 276-277.
• OLSON EO, SHEDD JD & ENGSTROM TN. 2016. A field inventory and collections summary of herpetofauna from the sutter buttes, an “Inland Island” within California’s Great Central Valley. West N Am Nat 76: 352-366.
• OSGOOD DW. 1970. Thermoregulation in water snakes studied by telemetry. Copeia, 1970: 568-571.
• PAGE MJ ET AL. 2021. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. PLoS Med 18: e1003583.
• PARK I-K, JEONG H & PARK D. 2022. A field evaluation of two external transmitter attachment methods for small snakes. J Ecol Environ 46: 1-7.
• PERKINS MW, CLOYED CS & EASON PK. 2020. Intraspecific dietary variation in niche partitioning within a community of ecologically similar snakes. Evol Ecol 34: 1017-1035.
• POUGH FH. 1966. Ecological relationships of rattlesnakes in southeastern Arizona with notes on other species. Copeia 1966: 676-683.
• POUGH FH. 1970. A quick method for permanently marking snakes and turtles. Herpetologica, 26: 428-430.
• PRATT KL, CAMPBELL HA, WATTS ME & FRANKLIN CE. 2010. Environmental and ecological factors influencing dive behaviour in the freshwater snake Acrochordus arafurae: a field-based telemetric study. Mar Freshw Res 61: 560-567.
• PRIOR KA & SHILTON CM. 1996. Post-Hibernation Mortality in Black Rat Snakes, Elaphe o. obsoleta J Herpetol 30: 275-278.
• REED RN, HART KM, RODDA GH, MAZZOTTI FJ, SNOW RW, CHERKISS M, ROZAR M & GOETZ S. 2011. A field test of attractant traps for invasive Burmese pythons (Python molurus bivittatus) in southern Florida. Wildl Res 38: 114-121.
• REYNOLDS RG, REGER ME, PEEK KJ, RAPHAEL BL, COLOSIMO G, MILLER AH, VANERELLI AA & GERBER GP. 2023. Spatial ecology of the Turks and Caicos Boa Chilabothrus c. chrysogaster Cope, 1871 (Serpentes: Boidae). Herpetol J 34: 22-34.
• RIEDLE JD. 2014. Demography of an urban population of ring-necked snakes (Diadophis punctatus) in Missouri. Herpetol Conserv Biol 9: 278-284.
• RILEY JL, BAXTER-GILBERT JH & LITZGUS JD. 2017. A comparison of three external transmitter attachment methods for snakes. Wildl Soc Bull 41: 132-139.
• ROARK AW & DORCAS ME. 2000. Regional body temperature variation in corn snakes measured using Temperature-Sensitive passive Integrated transponders. J Herpetol 34: 481-485.
• ROBINSON CJ, VIERNES MC, REED R, YACKEL A & NAFUS MG. 2018. Assessment of two external transmitter attachment methods for Boiga irregularis (Brown Treesnakes). Herpetol Rev 49: 32-34.
• RODDA GH, FARLEY JL, BISCHOF R & REED RN. 2007. New developments in snake barrier technology: Flyash covered wall offers a feasible alternative for permanent barriers to brown treesnakes (Boiga irregularis). Herpetol Conserv Biol 2: 157-163.
• ROSE JP, ERSAN JS, WYLIE GD, CASAZZA ML & HALSTEAD BJ. 2018. Reproductive frequency and size-dependence of fecundity in the Giant Gatersnake (Thamnophis gigas). Herpetol Conserv Biol 13: 80-90.
• ROSE JP, KIM R, SCHOENIG EJ, LIEN PC & HALSTEAD BJ. 2022. Integrating growth and survival models for flexible estimation of size-dependent survival in a cryptic, endangered snake. Ecol Evol 12: 12:e8799.
• ROTH ED & LUTTERSCHMIDT WI. 2011. Experimental validation of sex differences in spatial behavior patterns of Free-Ranging snakes: Implications for social interactions. Ethology 117: 852-858.
• RUBINOFF I, GRAHAM JB & MOTTA J. 1986. Diving of the sea snake Pelamis platurus in the Gulf of Panamá: I. Dive depth and duration. Mar Biol 91: 181-191.
• RUDOLPH DC, BURGDORF SJ, SCHAEFER RR, CONNER RN & ZAPPALORTI RT. 1998. Snake mortality associated with late season radio-transmitter implantation. Herpetol Rev 29: 155-156.
• RUDOLPH DC, SCHAEFER RR, SAENZ D & CONNER RN. 2004. Arboreal behavior in the timber rattlesnake, Crotalus horridus in eastern Texas. Tex J Sci 56: 395-404.
• SAENZ D, BURGDORF SJ, RUDOLPH DC & DURAN CM. 1996. Crotalus horridus (Timber Rattlesnake). Climbing. Herpetol Rev 27: 145.
• SAINT-GIRONS HS. 1981. Quelques observations sur la dispersion des nouveau-nés chez Vipera berus et Vipera aspis dans le bocage atlantique (Reptilia: Viperidae). Amphib-Reptil 2: 269-272.
• SAMPAIO ILR, SANTOS CP, FRANÇA RC, PEDROSA IMMC, SOLÉ M & FRANÇA FGR. 2018. Ecological diversity of a snake assemblage from the Atlantic Forest at the south coast of Paraíba, northeast Brazil. ZooKeys 787: 107-125.
• SANDFOSS M, MCBRIDE L, ANDERSON G, KISSEL A, MCCOLLISTER M, ROMAGOSA C & ADAMS AY. 2024. Flooding-induced failure of an invasive Burmese Python nest in southern Florida. Reptiles & Amphibians 31: e21384.
• SANTOS CM, DE MATTOS PIMENTA CA & NOBRE MRC. 2007. The PICO strategy for the research question construction and evidence search. Rev Lat Am Enfermagem 15: 508-511.
• SASAKI K & DUVALL D. 2003. Rainwater drinking by free-ranging japanese pitvipers, Gloydius blomhoffii. Curr Herpetol 22: 43-44.
• SAVARIE PJ, SHIVIK JA, WHITE GC, HURLEY JC & CLARK L. 2001. Use of acetaminophen for large-scale control of brown treesnakes. J Wildl Manage 65: 356-365.
• SHINE R & BONNET X. 2000. Snakes: a new “model organism” in ecological research? Trends Ecol Evol 15(6): 221-222.
• SHINE R, BROWN GP & GOIRAN C. 2021. Population dynamics of the sea snake Emydocephalus annulatus (Elapidae, Hydrophiinae). Sci Rep 11: 20701.
• SHINE R & GOIRAN C. 2021. Sexual dimorphism in size and shape of the head in the sea snake Emydocephalus annulatus (Hydrophiinae, Elapidae). Sci Rep 11: 20026.
• SHINE R, LANGKILDE T, WALL M & MASON RT. 2006. Temporal dynamics of emergence and dispersal of garter snakes from a communal den in Manitoba. Wildlife Res 33: 103-111.
• SHINE R & LI-XIN S. 2002. Arboreal ambush site selection by pit-vipers Gloydius shedaoensis Anim Behav 63: 565-576.
• SHINE R, O’CONNOR D, LEMASTER MP & MASON RT. 2001. Pick on someone your own size: ontogenetic shifts in mate choice by male garter snakes result in size-assortative mating. Anim Behav 61: 1133-1141.
• SHINE R, SHINE T, SHINE JM & SHINE BG. 2005. Synchrony in capture dates suggests cryptic social organization in sea snakes (Emydocephalus annulatus, Hydrophiidae). Austral Ecol 30: 805-811.
• SHINE R, SHINE TG, BROWN GP & GOIRAN C. 2020. Life history traits of the sea snake Emydocephalus annulatus, based on a 17-yr study. Coral Reefs 39: 1407-1414.
• SIERS SR ET AL. 2020. Automated Aerial Baiting for Invasive Brown Treesnake Control: System Overview and Program Status. In Proceedings of the Vertebrate Pest Conference, p. 1-6. California.
• SILVA WM, ARAUJO PF, FRANCA RC, PEDROSA IMMC & FRANÇA FGR. 2020. Use of the spool-and-line technique for studying microhabitat selection and daily movement of snakes in the Atlantic Forest of Brazil. Salamandra 56: 405-410.
• SILVY NJ, LOPEZ RR & PETERSON MJ. 2005. Wildlife marking techniques. In: Braun C (Ed), Techniques for wildlife investigations and management, Bethesda: Wildlife Society, Maryland, USA, p. 339-376.
• SILVY NJ, LOPEZ RR & PETERSON MJ. 2012. Techniques for marking wildlife. In: Silvy NJ (Ed), The wildlife techniques manual, Baltimore: John Hopkins University Press, Maryland, USA, p. 230-257.
• SKINNER M, HAZELL M, JAMESON J & LOUGHEED SC. 2024. Social networks reveal sex- and age-patterned social structure in Butler’s gartersnakes (Thamnophis butleri). Behav Ecol 35: arad095.
• SKINNER M & MILLER N. 2020. Aggregation and social interaction in garter snakes (Thamnophis sirtalis sirtalis). Behav Ecol Sociobiol 74: 1-13.
• SMITH BJ, CHERKISS MS, HART KM, ROCHFORD MR, SELBY TH, SNOW RW & MAZZOTTI FJ. 2016. Betrayal: radio-tagged burmese pythons reveal locations of conspecifics in Everglades National Park. Biol Invasions 18: 3239-3250.
• SMITH BJ, HART KM, MAZZOTTI FJ, BASILLE M & ROMAGOSA CM. 2018. Evaluating GPS biologging technology for studying spatial ecology of large constricting snakes. Anim Biotelemetry 6: 1-13.
• SMITH D, WEISSER M, CREAMER D, MCLARTY RJ & GALLAGHER GR. 2017. Field evaluation of two external attachment location of radio transmitters on non-venomous rat snakes (Elaphe obsolete). J Ecol Environ 46: 1-7.
• SMITH LJ, HOLYCROSS AT, PAINTER CW & DOUGLAS ME. 2001. Montane rattlesnakes and prescribed fire. Southw Naturalist 46: 54-61.
• SOCHA JJ, MIKLASZ K, JAFARI F & VLACHOS PP. 2010. Non-equilibrium trajectory dynamics and the kinematics of gliding in a flying snake. Bioinspir Biomim 5: 045002.
• SOCHA JJ, O’DEMPSEY T & LABARBERA M. 2005. A 3-D kinematic analysis of gliding in a flying snake,Chrysopelea paradisi. J Exp Biol 208: 1817-1833.
• SPENCER MM, LARDNER B, MAZUREK MJ & REED RN. 2015. Factors affecting defensive strike behavior in brown treesnakes (Boiga irregularis) provoked by humans. Herpetol Conserv Biol 10: 703-710.
• STANLEY JW & TRAUTH SE. 2007. Distribution of the queen snake (Regina septemvittata) in Arkansas. JAAS 61: 99-103.
• STERIJOVSKI B, AJTIĆ R, TOMOVIĆ L & BONNET X. 2014. Conservation threats to dice snakes (Natrix tessellata) in golem grad island (fyr of Macedonia). Herpetol Conserv Biol 9: 468-474.
• STERIJOVSKI B ET AL. 2011. Natrix tessellata on Golem Grad, FYR of Macedonia: a natural fortress shelters a prosperous snake population. Mertensiella 18: 298-301.
• STRINE C, SILVA I, NADOLSKI B, CRANE M, BARNES C, ARTCHAWAKOM T, HILL J & SUWANWAREE P. 2015. Sexual dimorphism of tropical green pit viper Trimeresurus (Cryptelytrops) macrops in Northeast Thailand. Amphib-Reptil 36: 327-338.
• SUBACH A, AVIDOV B, DORFMAN A & SCHARF I. 2021. Movement ecology and foraging behavior of the Saharan horned viper in the Negev Desert-an outline for research.
• TAGGART PL, MORRIS S & CARAGUEL CGB. 2021. The impact of PIT tags on the growth and survival of Pythons is insignificant in randomised controlled trial. PeerJ 9: e11531.
• TEFFO TR, KATONA K, BABOCSAY G, SÓS E & HALPERN B. 2023. Home Range of the Caspian Whipsnake Dolichophis caspius (Gmelin, 1789) in a Threatened Peri-Urban Population. Animals 13: 424-447.
• THOMAS LA & EKLUND CM. 1962. Overwintering of Western Equine Encephalomyelitis Virus in Garter Snakes Experimentally Infected by Culex tarsalis. Exp Biol Med 109: 421-424.
• TITLE PO ET AL. 2024. The macroevolutionary singularity of snakes. Science 383: 918-923.
• TODD BD, WILLSON JD, WINNE CT & GIBBONS JW. 2008. Aspects of the Ecology of the Earth Snakes (Virginia valeriae and V. striatula) in the Upper Coastal Plain. SENA 7: 349-358.
• TOZETTI AM & MARTINS M. 2007. A technique for external Radio-Transmitter attachment and the use of Thread-Bobbins for studying snake movements. SAJH 2: 184-190.
• TOZETTI AM, VETTORAZZO V & MARTINS M. 2009. Short-term movements of the South American rattlesnake (Crotalus durissus) in southeastern Brazil. Herpetol J 19: 201-206.
• TROAST S, DURSO AM, DURSO KP, METCALF MATTHEW & GUNNELS CW. 2022. Using Visible Implant Elastomer (VIE) to Mark Indotyphlops braminus (Brahminy Blindsnake). Herpetol Rev 53: 592-595.
• TSAIRI H & BOUSKILA A. 2004. Ambush site selection of a desert snake (Echis coloratus) at an oasis. Herpetologica 60: 13-23.
• TULLY T, GALLIARD JL & BARON J. 2020. Micro-geographic shift between negligible and actuarial senescence in a wild snake. J Anim Ecol 89: 2704-2716.
• TURNER GS. 2023. An analysis of aggregations in the little whip snake ’Suta flagellum’ (Elapidae). Vic Nat 140: 4-19.
• TYRRELL CL, CHRISTY MT, RODDA GH, ADAMS AY, ELLINGSON AR, SAVIDGE JA, DEAN-BRADLEY K & BISCHOF R. 2009. Evaluation of trap capture in a geographically closed population of brown treesnakes on Guam. J Appl Ecol 46: 128-135.
• UDYAWER V, READ M, HAMANN M, SIMPFENDORFER CA & HEUPEL MR. 2015. Effects of environmental variables on the movement and space use of coastal sea snakes over multiple temporal scales. J Exp Mar Bio Ecol 473: 26-34.
• UDYAWER V, SIMPFENDORFER CA & HEUPEL MR. 2015b. Diel patterns in three-dimensional use of space by sea snakes. Anim Biotelemetry 3: 1-9.
• UDYAWER V, SIMPFENDORFER CA, HEUPEL MR & CLARK TD. 2017. Temporal and spatial activity-associated energy partitioning in free-swimming sea snakes. Funct Ecol 31: 1739-1749.
• UETZ P, FREED P, AGUILAR R, REYES F, KUDERA J & HOŠEK J. 2025. How many species. The reptile database. Available at http://www.reptile-database.org/db-info/SpeciesStat.html Access 01/16/2025.
  » http://www.reptile-database.org/db-info/SpeciesStat.html
• UJVARI B, ANDERSSON S, BROWN G, SHINE R & MADSEN T. 2009. Climate-driven impacts of prey abundance on the population structure of a tropical aquatic predator. Oikos 119: 188-196.
• UJVARI B, BROWN G, SHINE R & MADSEN T. 2015. Floods and famine: climate-induced collapse of a tropical predator-prey community. Funct Ecol 30: 453-458.
• VANEK JP & BURKE RL. 2019. Insular dwarfism in female Eastern Hog-nosed Snakes (Heterodon platirhinos; Dipsadidae) on a barrier island. Can J Zool 98: 157-164.
• VORIS HK. 1985. Population size estimates for a marine snake (Enhydrina schistosa) in Malaysia. Copeia 1985: 955-961.
• WADDELL E, WHITWORTH A & MACLEOD R. 2016. A first test of the thread bobbin tracking technique as a method for studying the ecology of herpetofauna in a tropical rainforest. Herpetol Conserv Biol 11: 61-71.
• WEARY GC. 1969. An improved method of marking snakes. Copeia 1969: 854-855.
• WELSH HH, WHEELER CA & LIND AJ. 2010. Spatial Ecology of the Oregon Gartersnake, Thamnophis atratus hydrophilus, in a Free-Flowing Stream Environment. Copeia 2010: 75-85.
• WHITING MJ, DIXON JR, GREENE BD, MUELLER JM, THORNTON OW, HATFIELD JS, NICHOLS JD & HINES JE. 2008. Population dynamics of the Concho Water Snake in rivers and reservoirs. Copeia 2008: 438-445.
• WINNE CT, WILLSON JD, ANDREWS KM & REED RN. 2006. Efficacy of marking snakes with disposable medical cautery units. Herpetol Rev 37: 52-54.
• WOLFE AK, FLEMING PA & BATEMAN PW. 2018. Impacts of translocation on a large urban-adapted venomous snake. Wildlife Res 45: 316-324.
• WOOD DA, ROSE JP, HALSTEAD BJ, STOELTING RE, SWAIM KE & VANDERGAST AG. 2020. Combining genetic and demographic monitoring better informs conservation of an endangered urban snake. PLoS ONE 15: e0231744.
• WOODBURY AM. 1948. Marking Reptiles with an Electric Tattooing Outfit. Copeia 1948: 127-128.
• ZAHER H ET AL. 2019. Large-scale molecular phylogeny, morphology, divergence-time estimation, and the fossil record of advanced caenophidian snakes (Squamata: Serpentes). PLoS ONE 14: e0216148.

Edited by

• Handling editor
  Mirco Solé

Data availability

The data supporting the findings of this study are available within the article and its Supplementary Material.

Publication Dates

• Publication in this collection
  24 Aug 2026
• Date of issue
  2026

History

• Received
  5 Apr 2025
• Accepted
  3 Apr 2026